From a8f79980de88403a680b7e7a22a323aaf68f10f6 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 3 Sep 2021 16:29:18 -0700
Subject: [PATCH 01/34] XLSX support with ExcelJS

---
 src/dependencies.js   |   1 +
 src/fileAttachment.js |   7 ++-
 src/xlsx.js           | 100 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 107 insertions(+), 1 deletion(-)
 create mode 100644 src/xlsx.js

diff --git a/src/dependencies.js b/src/dependencies.js
index ae845fc3..e721f673 100644
--- a/src/dependencies.js
+++ b/src/dependencies.js
@@ -16,3 +16,4 @@ export const vegaliteApi = dependency("vega-lite-api", "5.0.0", "build/vega-lite
 export const arrow = dependency("apache-arrow", "4.0.1", "Arrow.es2015.min.js");
 export const arquero = dependency("arquero", "4.8.4", "dist/arquero.min.js");
 export const topojson = dependency("topojson-client", "3.1.0", "dist/topojson-client.min.js");
+export const exceljs = dependency("exceljs", "4.3.0", "dist/exceljs.min.js");
diff --git a/src/fileAttachment.js b/src/fileAttachment.js
index ac2c4d44..d185dded 100644
--- a/src/fileAttachment.js
+++ b/src/fileAttachment.js
@@ -1,7 +1,8 @@
 import {autoType, csvParse, csvParseRows, tsvParse, tsvParseRows} from "d3-dsv";
 import {require as requireDefault} from "d3-require";
-import {arrow, jszip} from "./dependencies.js";
+import {arrow, jszip, exceljs} from "./dependencies.js";
 import {SQLiteDatabaseClient} from "./sqlite.js";
+import {ExcelWorkbook} from "./xlsx.js";
 
 async function remote_fetch(file) {
   const response = await fetch(await file.url());
@@ -70,6 +71,10 @@ class AbstractFile {
   async html() {
     return this.xml("text/html");
   }
+  async xlsx() {
+    const [ExcelJS, buffer] = await Promise.all([requireDefault(exceljs.resolve()), this.arrayBuffer()]);
+    return new ExcelWorkbook(await new ExcelJS.Workbook().xlsx.load(buffer));
+  }
 }
 
 class FileAttachment extends AbstractFile {
diff --git a/src/xlsx.js b/src/xlsx.js
new file mode 100644
index 00000000..8075eff2
--- /dev/null
+++ b/src/xlsx.js
@@ -0,0 +1,100 @@
+export class ExcelWorkbook {
+  constructor(workbook) {
+    Object.defineProperty(this, "_", {value: workbook});
+  }
+  sheetNames() {
+    return this._.worksheets.map(sheet => sheet.name);
+  }
+  sheet(name, options) {
+    name = (typeof name === "number") ? name = this.sheetNames()[name] : name + "";
+    const sheet = this._.getWorksheet(name);
+    if (!sheet) throw new Error(`Sheet not found: ${name}`);
+    return extract(sheet, options);
+  }
+}
+
+function extract(sheet, options = {}) {
+  const { range, headers = false } = options;
+  let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
+  const empty = {};
+  const output = new Array(r1 - r0).fill(empty);
+
+  const headerRow = headers && sheet._rows[r0++];
+  const seen = new Set();
+  const names = [];
+  function name(n) {
+    if (!names[n]) {
+      let name = (headerRow ? valueOf(headerRow._cells[n]) : AA(n)) || AA(n);
+      while (seen.has(name)) name += "_";
+      seen.add((names[n] = name));
+    }
+    return names[n];
+  }
+
+  for (let r = r0; r < r1; r++) {
+    const _row = sheet._rows[r];
+    if (!_row || !_row.hasValues) continue;
+    const row = (output[r - r0] = {});
+    for (let c = c0; c < c1; c++) {
+      const value = valueOf(_row._cells[c]);
+      if (value) row[name(c)] = value;
+    }
+  }
+
+  output.columns = names.filter(() => true);
+  return output;
+}
+
+function valueOf(cell) {
+  if (!cell) return;
+  const { value } = cell;
+  if (value && typeof value === "object") {
+    if (value.formula) return value.result;
+    if (value.richText) return value.richText.map((d) => d.text).join("");
+    if (value.text && value.hyperlink)
+      return `<a href="${value.hyperlink}">${value.text}</a>`;
+  }
+  return value;
+}
+
+function parseRange(specifier = {}, { columnCount, rowCount }) {
+  if (typeof specifier === "string") {
+    const [
+      [c0 = 0, r0 = 0] = [],
+      [c1 = columnCount, r1 = rowCount] = []
+    ] = specifier.split(":").map(NN);
+    return [
+      [c0, r0],
+      [c1, r1]
+    ];
+  } else if (typeof specifier === "object") {
+    const {
+      start: [c0 = 0, r0 = 0] = [],
+      end: [c1 = columnCount, r1 = rowCount] = []
+    } = specifier;
+    return [
+      [c0, r0],
+      [c1, r1]
+    ];
+  }
+}
+
+function AA(x) {
+  let s = "";
+  x++;
+  do {
+    s = String.fromCharCode(64 + (x % 26 || 26)) + s;
+  } while ((x = Math.floor((x - 1) / 26)));
+  return s;
+}
+
+function NN(s = "") {
+  const [, sc, sr] = s.match(/^([a-zA-Z]+)?(\d+)?$/);
+  let c = undefined;
+  if (sc) {
+    c = 0;
+    for (let i = 0; i < sc.length; i++)
+      c += Math.pow(26, sc.length - i - 1) * (sc.charCodeAt(i) - 64);
+  }
+  return [c && c - 1, sr && +sr - 1];
+}

From 38fceabc8493a9e169d49ce27555d4c4b3b67774 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 3 Sep 2021 16:37:41 -0700
Subject: [PATCH 02/34] Prettier

---
 src/xlsx.js | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 8075eff2..039c3da8 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -3,18 +3,19 @@ export class ExcelWorkbook {
     Object.defineProperty(this, "_", {value: workbook});
   }
   sheetNames() {
-    return this._.worksheets.map(sheet => sheet.name);
+    return this._.worksheets.map((sheet) => sheet.name);
   }
   sheet(name, options) {
-    name = (typeof name === "number") ? name = this.sheetNames()[name] : name + "";
-    const sheet = this._.getWorksheet(name);
+    const sheet = this._.getWorksheet(
+      typeof name === "number" ? this.sheetNames()[name] : name + ""
+    );
     if (!sheet) throw new Error(`Sheet not found: ${name}`);
     return extract(sheet, options);
   }
 }
 
 function extract(sheet, options = {}) {
-  const { range, headers = false } = options;
+  const {range, headers = false} = options;
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
   const empty = {};
   const output = new Array(r1 - r0).fill(empty);
@@ -47,7 +48,7 @@ function extract(sheet, options = {}) {
 
 function valueOf(cell) {
   if (!cell) return;
-  const { value } = cell;
+  const {value} = cell;
   if (value && typeof value === "object") {
     if (value.formula) return value.result;
     if (value.richText) return value.richText.map((d) => d.text).join("");
@@ -57,24 +58,22 @@ function valueOf(cell) {
   return value;
 }
 
-function parseRange(specifier = {}, { columnCount, rowCount }) {
+function parseRange(specifier = {}, {columnCount, rowCount}) {
   if (typeof specifier === "string") {
-    const [
-      [c0 = 0, r0 = 0] = [],
-      [c1 = columnCount, r1 = rowCount] = []
-    ] = specifier.split(":").map(NN);
+    const [[c0 = 0, r0 = 0] = [], [c1 = columnCount, r1 = rowCount] = []] =
+      specifier.split(":").map(NN);
     return [
       [c0, r0],
-      [c1, r1]
+      [c1, r1],
     ];
   } else if (typeof specifier === "object") {
     const {
       start: [c0 = 0, r0 = 0] = [],
-      end: [c1 = columnCount, r1 = rowCount] = []
+      end: [c1 = columnCount, r1 = rowCount] = [],
     } = specifier;
     return [
       [c0, r0],
-      [c1, r1]
+      [c1, r1],
     ];
   }
 }

From 922644606239b3bef5d6955f495da5ca66909ac3 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Sat, 4 Sep 2021 14:29:38 -0700
Subject: [PATCH 03/34] Change range option to nested arrays

General code clean up
---
 src/xlsx.js | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 039c3da8..920a5dd3 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -5,20 +5,18 @@ export class ExcelWorkbook {
   sheetNames() {
     return this._.worksheets.map((sheet) => sheet.name);
   }
-  sheet(name, options) {
+  sheet(name, {range, headers = false} = {}) {
     const sheet = this._.getWorksheet(
       typeof name === "number" ? this.sheetNames()[name] : name + ""
     );
     if (!sheet) throw new Error(`Sheet not found: ${name}`);
-    return extract(sheet, options);
+    return extract(sheet, {range, headers});
   }
 }
 
-function extract(sheet, options = {}) {
-  const {range, headers = false} = options;
+function extract(sheet, {range, headers}) {
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
-  const empty = {};
-  const output = new Array(r1 - r0).fill(empty);
+  const output = new Array(r1 - r0).fill({});
 
   const headerRow = headers && sheet._rows[r0++];
   const seen = new Set();
@@ -58,7 +56,7 @@ function valueOf(cell) {
   return value;
 }
 
-function parseRange(specifier = {}, {columnCount, rowCount}) {
+function parseRange(specifier = [], {columnCount, rowCount}) {
   if (typeof specifier === "string") {
     const [[c0 = 0, r0 = 0] = [], [c1 = columnCount, r1 = rowCount] = []] =
       specifier.split(":").map(NN);
@@ -67,10 +65,8 @@ function parseRange(specifier = {}, {columnCount, rowCount}) {
       [c1, r1],
     ];
   } else if (typeof specifier === "object") {
-    const {
-      start: [c0 = 0, r0 = 0] = [],
-      end: [c1 = columnCount, r1 = rowCount] = [],
-    } = specifier;
+    const [[c0 = 0, r0 = 0] = [], [c1 = columnCount, r1 = rowCount] = []] =
+      specifier;
     return [
       [c0, r0],
       [c1, r1],
@@ -78,13 +74,13 @@ function parseRange(specifier = {}, {columnCount, rowCount}) {
   }
 }
 
-function AA(x) {
-  let s = "";
-  x++;
+function AA(c) {
+  let sc = "";
+  c++;
   do {
-    s = String.fromCharCode(64 + (x % 26 || 26)) + s;
-  } while ((x = Math.floor((x - 1) / 26)));
-  return s;
+    sc = String.fromCharCode(64 + (c % 26 || 26)) + sc;
+  } while ((c = Math.floor((c - 1) / 26)));
+  return sc;
 }
 
 function NN(s = "") {

From 77159f0220876ee704646cb51d3b0e894a81308a Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Sat, 4 Sep 2021 22:23:53 -0700
Subject: [PATCH 04/34] Tests and bug fixes

---
 src/xlsx.js       |  21 ++++---
 test/xlsx-test.js | 156 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 168 insertions(+), 9 deletions(-)
 create mode 100644 test/xlsx-test.js

diff --git a/src/xlsx.js b/src/xlsx.js
index 920a5dd3..fd3a53e2 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -16,8 +16,6 @@ export class ExcelWorkbook {
 
 function extract(sheet, {range, headers}) {
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
-  const output = new Array(r1 - r0).fill({});
-
   const headerRow = headers && sheet._rows[r0++];
   const seen = new Set();
   const names = [];
@@ -30,13 +28,14 @@ function extract(sheet, {range, headers}) {
     return names[n];
   }
 
-  for (let r = r0; r < r1; r++) {
+  const output = new Array(r1 - r0 + 1).fill({});
+  for (let r = r0; r <= r1; r++) {
     const _row = sheet._rows[r];
     if (!_row || !_row.hasValues) continue;
     const row = (output[r - r0] = {});
-    for (let c = c0; c < c1; c++) {
+    for (let c = c0; c <= c1; c++) {
       const value = valueOf(_row._cells[c]);
-      if (value) row[name(c)] = value;
+      if (value !== null && value !== undefined) row[name(c)] = value;
     }
   }
 
@@ -58,15 +57,19 @@ function valueOf(cell) {
 
 function parseRange(specifier = [], {columnCount, rowCount}) {
   if (typeof specifier === "string") {
-    const [[c0 = 0, r0 = 0] = [], [c1 = columnCount, r1 = rowCount] = []] =
-      specifier.split(":").map(NN);
+    const [
+      [c0 = 0, r0 = 0] = [],
+      [c1 = columnCount - 1, r1 = rowCount - 1] = [],
+    ] = specifier.split(":").map(NN);
     return [
       [c0, r0],
       [c1, r1],
     ];
   } else if (typeof specifier === "object") {
-    const [[c0 = 0, r0 = 0] = [], [c1 = columnCount, r1 = rowCount] = []] =
-      specifier;
+    const [
+      [c0 = 0, r0 = 0] = [],
+      [c1 = columnCount - 1, r1 = rowCount - 1] = [],
+    ] = specifier;
     return [
       [c0, r0],
       [c1, r1],
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
new file mode 100644
index 00000000..940cea98
--- /dev/null
+++ b/test/xlsx-test.js
@@ -0,0 +1,156 @@
+import {test} from "tap";
+import {ExcelWorkbook} from "../src/xlsx.js";
+
+function mockWorkbook(contents) {
+  return {
+    worksheets: Object.keys(contents).map((name) => ({name})),
+    getWorksheet(name) {
+      const _rows = contents[name];
+      return {
+        _rows: _rows.map((row) => ({
+          _cells: row.map((cell) => ({value: cell})),
+          hasValues: !!row.length,
+        })),
+        rowCount: _rows.length,
+        columnCount: Math.max(..._rows.map((r) => r.length)),
+      };
+    },
+  };
+}
+
+test("FileAttachment.xlsx reads sheet names", (t) => {
+  const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
+  t.same(workbook.sheetNames(), ["Sheet1"]);
+  t.end();
+});
+
+test("FileAttachment.xlsx reads sheets", (t) => {
+  const workbook = new ExcelWorkbook(
+    mockWorkbook({
+      Sheet1: [
+        ["one", "two", "three"],
+        [1, 2, 3],
+      ],
+    })
+  );
+  t.same(workbook.sheet(0), [
+    {A: "one", B: "two", C: "three"},
+    {A: 1, B: 2, C: 3},
+  ]);
+  t.end();
+});
+
+test("FileAttachment.xlsx reads sheets with different types", (t) => {
+  const workbook = new ExcelWorkbook(
+    mockWorkbook({
+      Sheet1: [
+        ["one", {richText: [{text: "two"}, {text: "three"}]}],
+        [
+          {text: "link", hyperlink: "https://example.com"},
+          2,
+          {formula: "=B2*5", result: 10},
+        ],
+      ],
+    })
+  );
+  t.same(workbook.sheet(0), [
+    {A: "one", B: "twothree"},
+    {A: `<a href="https://example.com">link</a>`, B: 2, C: 10},
+  ]);
+  t.end();
+});
+
+test("FileAttachment.xlsx reads sheets with headers", (t) => {
+  const workbook = new ExcelWorkbook(
+    mockWorkbook({
+      Sheet1: [
+        ["one", "one", "one", "two"],
+        [1, null, 3, 4],
+        [5, 6, 7, 8],
+      ],
+    })
+  );
+  t.same(workbook.sheet(0, {headers: true}), [
+    {one: 1, one_: 3, two: 4},
+    {one: 5, one__: 6, one_: 7, two: 8},
+  ]);
+  t.end();
+});
+
+test("FileAttachment.xlsx reads sheet ranges", (t) => {
+  const workbook = new ExcelWorkbook(
+    mockWorkbook({
+      Sheet1: [
+        [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+        [10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
+        [20, 21, 22, 23, 24, 25, 26, 27, 28, 29],
+        [30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
+      ],
+    })
+  );
+
+  // undefined
+  // ""
+  // []
+  const entireSheet = [
+    {A: 0, B: 1, C: 2, D: 3, E: 4, F: 5, G: 6, H: 7, I: 8, J: 9},
+    {A: 10, B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
+    {A: 20, B: 21, C: 22, D: 23, E: 24, F: 25, G: 26, H: 27, I: 28, J: 29},
+    {A: 30, B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
+  ];
+  t.same(workbook.sheet(0), entireSheet);
+  t.same(workbook.sheet(0, {range: ""}), entireSheet);
+  t.same(workbook.sheet(0, {range: []}), entireSheet);
+
+  // "B2:C3"
+  // [[1,1],[2,2]]
+  t.same(workbook.sheet(0, {range: "B2:C3"}), [
+    {B: 11, C: 12},
+    {B: 21, C: 22},
+  ]);
+  t.same(
+    workbook.sheet(0, {
+      range: [
+        [1, 1],
+        [2, 2],
+      ],
+    }),
+    [
+      {B: 11, C: 12},
+      {B: 21, C: 22},
+    ]
+  );
+
+  // ":C3"
+  // [,[2,2]]
+  t.same(workbook.sheet(0, {range: ":C3"}), [
+    {A: 0, B: 1, C: 2},
+    {A: 10, B: 11, C: 12},
+    {A: 20, B: 21, C: 22},
+  ]);
+  t.same(workbook.sheet(0, {range: [undefined, [2, 2]]}), [
+    {A: 0, B: 1, C: 2},
+    {A: 10, B: 11, C: 12},
+    {A: 20, B: 21, C: 22},
+  ]);
+
+  // "B2"
+  // [[1,1]]
+  t.same(workbook.sheet(0, {range: "B2"}), [
+    {B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
+    {B: 21, C: 22, D: 23, E: 24, F: 25, G: 26, H: 27, I: 28, J: 29},
+    {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
+  ]);
+  t.same(workbook.sheet(0, {range: [[1, 1]]}), [
+    {B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
+    {B: 21, C: 22, D: 23, E: 24, F: 25, G: 26, H: 27, I: 28, J: 29},
+    {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
+  ]);
+
+  // "2"
+  // [[,1]]
+  t.same(workbook.sheet(0, {range: "2"}), entireSheet.slice(1));
+  t.same(workbook.sheet(0, {range: [[undefined, 1]]}), entireSheet.slice(1));
+
+  t.end();
+});

From d8904d0e6a28546aa0f03cdcfd927fada8fa638d Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Sun, 5 Sep 2021 13:36:00 -0700
Subject: [PATCH 05/34] Respect header row order when resolving conflicts

---
 src/xlsx.js       |  3 ++-
 test/xlsx-test.js | 10 +++++-----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index fd3a53e2..cc6528da 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -16,9 +16,9 @@ export class ExcelWorkbook {
 
 function extract(sheet, {range, headers}) {
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
-  const headerRow = headers && sheet._rows[r0++];
   const seen = new Set();
   const names = [];
+  const headerRow = headers && sheet._rows[r0++];
   function name(n) {
     if (!names[n]) {
       let name = (headerRow ? valueOf(headerRow._cells[n]) : AA(n)) || AA(n);
@@ -27,6 +27,7 @@ function extract(sheet, {range, headers}) {
     }
     return names[n];
   }
+  if (headerRow) for (let c = c0; c <= c1; c++) name(c);
 
   const output = new Array(r1 - r0 + 1).fill({});
   for (let r = r0; r <= r1; r++) {
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 940cea98..60a622ba 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -64,15 +64,15 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
   const workbook = new ExcelWorkbook(
     mockWorkbook({
       Sheet1: [
-        ["one", "one", "one", "two"],
-        [1, null, 3, 4],
-        [5, 6, 7, 8],
+        [null, "one", "one", "two", "A"],
+        [   1,  null,     3,     4,   5],
+        [   6,     7,     8,     9,  10],
       ],
     })
   );
   t.same(workbook.sheet(0, {headers: true}), [
-    {one: 1, one_: 3, two: 4},
-    {one: 5, one__: 6, one_: 7, two: 8},
+    {A: 1, one_: 3, two: 4, A_: 5},
+    {A: 6, one: 7, one_: 8, two: 9, A_: 10},
   ]);
   t.end();
 });

From ee0dfbf2d57e7328d7c9e04a6c53bb401b5e24ab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Rivi=C3=A8re?= <fil@rezo.net>
Date: Tue, 7 Sep 2021 19:58:20 +0200
Subject: [PATCH 06/34] Fil/xlsx (#249)

* document xlsx (minimalist, we'll work on the notebook first)

* fix coverage reporter

(avoids a crash on my computer; solution found at https://github.com/tapjs/node-tap/issues/624)

* unknown sheet name

* simplify rows naming

* NN is always called on string (cell specifier such as "AA99")

* test name

* more range specifiers
---
 README.md         |  4 ++++
 package.json      |  2 +-
 src/xlsx.js       | 34 ++++++++++++++----------------
 test/xlsx-test.js | 53 +++++++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 72 insertions(+), 21 deletions(-)

diff --git a/README.md b/README.md
index a5ffdffe..5a2387ee 100644
--- a/README.md
+++ b/README.md
@@ -379,6 +379,10 @@ Returns a promise to the file loads as a [SQLite database client](https://observ
 const db = await FileAttachment("chinook.db").sqlite();
 ```
 
+<a href="#attachment_xlsx" name="attachment_xlsx">#</a> *attachment*.<b>xlsx</b>() [<>](https://github.com/observablehq/stdlib/blob/master/src/xlsx.js "Source")
+
+Returns a promise to the file loaded as an [ExcelWorkbook](https://observablehq.com/@observablehq/excelworkbook).
+
 <a href="#FileAttachments" name="FileAttachments">#</a> <b>FileAttachments</b>(<i>resolve</i>) [<>](https://github.com/observablehq/stdlib/blob/master/src/fileAttachment.js "Source")
 
 *Note: this function is not part of the Observable standard library (in notebooks), but is provided by this module as a means for defining custom file attachment implementations when working directly with the Observable runtime.*
diff --git a/package.json b/package.json
index f7de5be5..e92ee190 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
     "url": "https://github.com/observablehq/stdlib.git"
   },
   "scripts": {
-    "test": "tap 'test/**/*-test.js'",
+    "test": "tap 'test/**/*-test.js' --reporter classic",
     "prepublishOnly": "rollup -c",
     "postpublish": "git push && git push --tags"
   },
diff --git a/src/xlsx.js b/src/xlsx.js
index cc6528da..688232f3 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -6,28 +6,24 @@ export class ExcelWorkbook {
     return this._.worksheets.map((sheet) => sheet.name);
   }
   sheet(name, {range, headers = false} = {}) {
-    const sheet = this._.getWorksheet(
-      typeof name === "number" ? this.sheetNames()[name] : name + ""
-    );
-    if (!sheet) throw new Error(`Sheet not found: ${name}`);
+    const names = this.sheetNames();
+    const sname = typeof name === "number" ? names[name] : names.includes(name + "") ? name + "" : null;
+    if (sname == null) throw new Error(`Sheet not found: ${name}`);
+    const sheet = this._.getWorksheet(sname);
     return extract(sheet, {range, headers});
   }
 }
 
 function extract(sheet, {range, headers}) {
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
-  const seen = new Set();
-  const names = [];
   const headerRow = headers && sheet._rows[r0++];
-  function name(n) {
-    if (!names[n]) {
-      let name = (headerRow ? valueOf(headerRow._cells[n]) : AA(n)) || AA(n);
-      while (seen.has(name)) name += "_";
-      seen.add((names[n] = name));
-    }
-    return names[n];
+  let names = new Set();
+  for (let n = c0; n <= c1; n++) {
+    let name = (headerRow ? valueOf(headerRow._cells[n]) : null) || AA(n);
+    while (names.has(name)) name += "_";
+    names.add(name);
   }
-  if (headerRow) for (let c = c0; c <= c1; c++) name(c);
+  names = new Array(c0).concat(Array.from(names));
 
   const output = new Array(r1 - r0 + 1).fill({});
   for (let r = r0; r <= r1; r++) {
@@ -36,7 +32,7 @@ function extract(sheet, {range, headers}) {
     const row = (output[r - r0] = {});
     for (let c = c0; c <= c1; c++) {
       const value = valueOf(_row._cells[c]);
-      if (value !== null && value !== undefined) row[name(c)] = value;
+      if (value != null) row[names[c]] = value;
     }
   }
 
@@ -75,6 +71,8 @@ function parseRange(specifier = [], {columnCount, rowCount}) {
       [c0, r0],
       [c1, r1],
     ];
+  } else {
+    throw new Error(`Unknown range specifier`);
   }
 }
 
@@ -87,13 +85,13 @@ function AA(c) {
   return sc;
 }
 
-function NN(s = "") {
-  const [, sc, sr] = s.match(/^([a-zA-Z]+)?(\d+)?$/);
+function NN(s) {
+  const [, sc, sr] = s.match(/^([A-Z]*)(\d*)$/i);
   let c = undefined;
   if (sc) {
     c = 0;
     for (let i = 0; i < sc.length; i++)
       c += Math.pow(26, sc.length - i - 1) * (sc.charCodeAt(i) - 64);
   }
-  return [c && c - 1, sr && +sr - 1];
+  return [c ? c - 1 : undefined, sr ? +sr - 1 : undefined];
 }
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 60a622ba..40ef8999 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -24,6 +24,12 @@ test("FileAttachment.xlsx reads sheet names", (t) => {
   t.end();
 });
 
+test("FileAttachment.xlsx sheet(name) throws on unknown sheet name", (t) => {
+  const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
+  t.throws(() => workbook.sheet("bad"));
+  t.end();
+});
+
 test("FileAttachment.xlsx reads sheets", (t) => {
   const workbook = new ExcelWorkbook(
     mockWorkbook({
@@ -37,6 +43,10 @@ test("FileAttachment.xlsx reads sheets", (t) => {
     {A: "one", B: "two", C: "three"},
     {A: 1, B: 2, C: 3},
   ]);
+  t.same(workbook.sheet("Sheet1"), [
+    {A: "one", B: "two", C: "three"},
+    {A: 1, B: 2, C: 3},
+  ]);
   t.end();
 });
 
@@ -44,18 +54,20 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
   const workbook = new ExcelWorkbook(
     mockWorkbook({
       Sheet1: [
-        ["one", {richText: [{text: "two"}, {text: "three"}]}],
+        ["one", null, {richText: [{text: "two"}, {text: "three"}]}, undefined],
         [
           {text: "link", hyperlink: "https://example.com"},
           2,
           {formula: "=B2*5", result: 10},
         ],
+        [],
       ],
     })
   );
   t.same(workbook.sheet(0), [
-    {A: "one", B: "twothree"},
+    {A: "one", C: "twothree"},
     {A: `<a href="https://example.com">link</a>`, B: 2, C: 10},
+    {},
   ]);
   t.end();
 });
@@ -152,5 +164,42 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   t.same(workbook.sheet(0, {range: "2"}), entireSheet.slice(1));
   t.same(workbook.sheet(0, {range: [[undefined, 1]]}), entireSheet.slice(1));
 
+  // ":I"
+  // [,[1,]]
+  const sheetJ = [
+    { I: 8, J: 9 },
+    { I: 18, J: 19 },
+    { I: 28, J: 29 },
+    { I: 38, J: 39 }
+  ];
+  t.same(workbook.sheet(0, {range: "I"}), sheetJ);
+  t.same(workbook.sheet(0, {range: [[8, undefined], undefined]}), sheetJ);
+  t.end();
+});
+
+test("FileAttachment.xlsx throws on unknown range specifier", (t) => {
+  const workbook = new ExcelWorkbook(mockWorkbook({ Sheet1: [] }));
+  t.throws(() => workbook.sheet(0, {range: 0}));
+  t.end();
+});
+
+test("FileAttachment.xlsx derives column names such as A AA AAA…", (t) => {
+  const l0 = 26 * 26 * 26 + 26 * 26 + 26;
+  const workbook = new ExcelWorkbook(
+    mockWorkbook({
+      Sheet1: [
+        Array.from({length: l0}).fill(1),
+      ],
+    })
+  );
+  t.same(workbook.sheet(0, {headers: false}).columns.filter(d => d.match(/^A*$/)), ["A", "AA", "AAA"]);
+  const workbook1 = new ExcelWorkbook(
+    mockWorkbook({
+      Sheet1: [
+        Array.from({length: l0 + 1}).fill(1),
+      ],
+    })
+  );
+  t.same(workbook1.sheet(0, {headers: false}).columns.filter(d => d.match(/^A*$/)), ["A", "AA", "AAA", "AAAA"]);
   t.end();
 });

From fd177b06265f8d73d890f0fee6c6fc2eec0b4f45 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Sun, 5 Sep 2021 13:53:54 -0700
Subject: [PATCH 07/34] Column only range test case

---
 test/xlsx-test.js | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 40ef8999..ec09b060 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -77,8 +77,8 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
     mockWorkbook({
       Sheet1: [
         [null, "one", "one", "two", "A"],
-        [   1,  null,     3,     4,   5],
-        [   6,     7,     8,     9,  10],
+        [1, null, 3, 4, 5],
+        [6, 7, 8, 9, 10],
       ],
     })
   );
@@ -159,6 +159,21 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
   ]);
 
+  // "H"
+  // [[7]]
+  t.same(workbook.sheet(0, {range: "H"}), [
+    {H: 7, I: 8, J: 9},
+    {H: 17, I: 18, J: 19},
+    {H: 27, I: 28, J: 29},
+    {H: 37, I: 38, J: 39},
+  ]);
+  t.same(workbook.sheet(0, {range: [[7]]}), [
+    {H: 7, I: 8, J: 9},
+    {H: 17, I: 18, J: 19},
+    {H: 27, I: 28, J: 29},
+    {H: 37, I: 38, J: 39},
+  ]);
+
   // "2"
   // [[,1]]
   t.same(workbook.sheet(0, {range: "2"}), entireSheet.slice(1));

From f6ddcff37ac935afd72bd67903d0922e6ce244a8 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 7 Sep 2021 16:51:00 -0700
Subject: [PATCH 08/34] sheetNames is enumerable

---
 src/xlsx.js       | 12 +++++++-----
 test/xlsx-test.js |  2 +-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 688232f3..e8fe016c 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -1,13 +1,15 @@
 export class ExcelWorkbook {
   constructor(workbook) {
     Object.defineProperty(this, "_", {value: workbook});
-  }
-  sheetNames() {
-    return this._.worksheets.map((sheet) => sheet.name);
+    this.sheetNames = this._.worksheets.map((sheet) => sheet.name);
   }
   sheet(name, {range, headers = false} = {}) {
-    const names = this.sheetNames();
-    const sname = typeof name === "number" ? names[name] : names.includes(name + "") ? name + "" : null;
+    const sname =
+      typeof name === "number"
+        ? this.sheetNames[name]
+        : this.sheetNames.includes(name + "")
+        ? name + ""
+        : null;
     if (sname == null) throw new Error(`Sheet not found: ${name}`);
     const sheet = this._.getWorksheet(sname);
     return extract(sheet, {range, headers});
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index ec09b060..1ebf0f4f 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -20,7 +20,7 @@ function mockWorkbook(contents) {
 
 test("FileAttachment.xlsx reads sheet names", (t) => {
   const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
-  t.same(workbook.sheetNames(), ["Sheet1"]);
+  t.same(workbook.sheetNames, ["Sheet1"]);
   t.end();
 });
 

From 9b9eab673fa637038bae3d06f6b7f83cd4cd5cc2 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Wed, 8 Sep 2021 16:01:44 -0700
Subject: [PATCH 09/34] One more test to check for empty columns

Prettier + use default/base tap reporter
---
 package.json      |  2 +-
 test/xlsx-test.js | 32 +++++++++++++++++++-------------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/package.json b/package.json
index e92ee190..10448e0b 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
     "url": "https://github.com/observablehq/stdlib.git"
   },
   "scripts": {
-    "test": "tap 'test/**/*-test.js' --reporter classic",
+    "test": "tap 'test/**/*-test.js' --reporter base",
     "prepublishOnly": "rollup -c",
     "postpublish": "git push && git push --tags"
   },
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 1ebf0f4f..e964ed7c 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -182,18 +182,22 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   // ":I"
   // [,[1,]]
   const sheetJ = [
-    { I: 8, J: 9 },
-    { I: 18, J: 19 },
-    { I: 28, J: 29 },
-    { I: 38, J: 39 }
+    {I: 8, J: 9},
+    {I: 18, J: 19},
+    {I: 28, J: 29},
+    {I: 38, J: 39},
   ];
   t.same(workbook.sheet(0, {range: "I"}), sheetJ);
   t.same(workbook.sheet(0, {range: [[8, undefined], undefined]}), sheetJ);
+
+  // ":ZZ" (doesn't cause extra column fields)
+  t.same(workbook.sheet(0, {range: ":ZZ"}), entireSheet);
+
   t.end();
 });
 
 test("FileAttachment.xlsx throws on unknown range specifier", (t) => {
-  const workbook = new ExcelWorkbook(mockWorkbook({ Sheet1: [] }));
+  const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
   t.throws(() => workbook.sheet(0, {range: 0}));
   t.end();
 });
@@ -202,19 +206,21 @@ test("FileAttachment.xlsx derives column names such as A AA AAA…", (t) => {
   const l0 = 26 * 26 * 26 + 26 * 26 + 26;
   const workbook = new ExcelWorkbook(
     mockWorkbook({
-      Sheet1: [
-        Array.from({length: l0}).fill(1),
-      ],
+      Sheet1: [Array.from({length: l0}).fill(1)],
     })
   );
-  t.same(workbook.sheet(0, {headers: false}).columns.filter(d => d.match(/^A*$/)), ["A", "AA", "AAA"]);
+  t.same(
+    workbook.sheet(0, {headers: false}).columns.filter((d) => d.match(/^A*$/)),
+    ["A", "AA", "AAA"]
+  );
   const workbook1 = new ExcelWorkbook(
     mockWorkbook({
-      Sheet1: [
-        Array.from({length: l0 + 1}).fill(1),
-      ],
+      Sheet1: [Array.from({length: l0 + 1}).fill(1)],
     })
   );
-  t.same(workbook1.sheet(0, {headers: false}).columns.filter(d => d.match(/^A*$/)), ["A", "AA", "AAA", "AAAA"]);
+  t.same(
+    workbook1.sheet(0, {headers: false}).columns.filter((d) => d.match(/^A*$/)),
+    ["A", "AA", "AAA", "AAAA"]
+  );
   t.end();
 });

From a8450868304f025d7a3540b9a8c6099908ee00b2 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 08:23:22 -0700
Subject: [PATCH 10/34] Add Node 16 to the test matrix

---
 .github/workflows/nodejs.yml | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index 10ca6b7f..2a2dcb19 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -4,23 +4,22 @@ on: [push]
 
 jobs:
   build:
-
     strategy:
       matrix:
         os: [ubuntu-latest]
-        node-version: [12.x, 14.x]
+        node-version: [12.x, 14.x, 16.x]
 
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v1
-    - name: Use Node.js ${{ matrix.node-version }}
-      uses: actions/setup-node@v1
-      with:
-        node-version: ${{ matrix.node-version }}
-    - name: yarn install and test
-      run: |
-        yarn install --frozen-lockfile
-        yarn test
-      env:
-        CI: true
+      - uses: actions/checkout@v1
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: yarn install and test
+        run: |
+          yarn install --frozen-lockfile
+          yarn test
+        env:
+          CI: true

From f30b626c0e4034ebc53ec7a0092512c77d5f1110 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 08:25:18 -0700
Subject: [PATCH 11/34] Revert reporter to classic for Node 16

---
 package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package.json b/package.json
index 10448e0b..e92ee190 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
     "url": "https://github.com/observablehq/stdlib.git"
   },
   "scripts": {
-    "test": "tap 'test/**/*-test.js' --reporter base",
+    "test": "tap 'test/**/*-test.js' --reporter classic",
     "prepublishOnly": "rollup -c",
     "postpublish": "git push && git push --tags"
   },

From e421983baf203f5f0c8299fd0cc4da3cc5ad3c98 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 08:26:37 -0700
Subject: [PATCH 12/34] Don't fail matrix quickly in actions

---
 .github/workflows/nodejs.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index 2a2dcb19..0e12497a 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -5,6 +5,7 @@ on: [push]
 jobs:
   build:
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest]
         node-version: [12.x, 14.x, 16.x]

From e8b0153d78d00fd6868672d0b8fe9401d5d3597c Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 09:08:48 -0700
Subject: [PATCH 13/34] More coverage.

---
 src/xlsx.js       |  9 ++++++---
 test/xlsx-test.js | 35 ++++++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index e8fe016c..7acf0ce9 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -48,8 +48,11 @@ function valueOf(cell) {
   if (value && typeof value === "object") {
     if (value.formula) return value.result;
     if (value.richText) return value.richText.map((d) => d.text).join("");
-    if (value.text && value.hyperlink)
-      return `<a href="${value.hyperlink}">${value.text}</a>`;
+    if (value.text)
+      return value.hyperlink
+        ? `<a href="${value.hyperlink}">${value.text}</a>`
+        : value.text;
+    return "";
   }
   return value;
 }
@@ -57,7 +60,7 @@ function valueOf(cell) {
 function parseRange(specifier = [], {columnCount, rowCount}) {
   if (typeof specifier === "string") {
     const [
-      [c0 = 0, r0 = 0] = [],
+      [c0 = 0, r0 = 0],
       [c1 = columnCount - 1, r1 = rowCount - 1] = [],
     ] = specifier.split(":").map(NN);
     return [
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index e964ed7c..85902da7 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -1,19 +1,19 @@
 import {test} from "tap";
 import {ExcelWorkbook} from "../src/xlsx.js";
 
-function mockWorkbook(contents) {
+function mockWorkbook(contents, overrides = {}) {
   return {
     worksheets: Object.keys(contents).map((name) => ({name})),
     getWorksheet(name) {
       const _rows = contents[name];
-      return {
+      return Object.assign({
         _rows: _rows.map((row) => ({
           _cells: row.map((cell) => ({value: cell})),
           hasValues: !!row.length,
         })),
         rowCount: _rows.length,
         columnCount: Math.max(..._rows.map((r) => r.length)),
-      };
+      }, overrides);
     },
   };
 }
@@ -56,17 +56,20 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
       Sheet1: [
         ["one", null, {richText: [{text: "two"}, {text: "three"}]}, undefined],
         [
+          {text: "plain text"},
           {text: "link", hyperlink: "https://example.com"},
           2,
           {formula: "=B2*5", result: 10},
         ],
+        [ {/* empty object */} ],
         [],
       ],
     })
   );
   t.same(workbook.sheet(0), [
     {A: "one", C: "twothree"},
-    {A: `<a href="https://example.com">link</a>`, B: 2, C: 10},
+    {A: "plain text", B: `<a href="https://example.com">link</a>`, C: 2, D: 10},
+    {A: ""},
     {},
   ]);
   t.end();
@@ -81,11 +84,19 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
         [6, 7, 8, 9, 10],
       ],
     })
+    // }, { columnCount: 10 })
   );
   t.same(workbook.sheet(0, {headers: true}), [
     {A: 1, one_: 3, two: 4, A_: 5},
     {A: 6, one: 7, one_: 8, two: 9, A_: 10},
   ]);
+  t.same(workbook.sheet(0, {headers: true}).columns, [
+    "A",
+    "one",
+    "one_",
+    "two",
+    "A_",
+  ]);
   t.end();
 });
 
@@ -113,6 +124,7 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   t.same(workbook.sheet(0), entireSheet);
   t.same(workbook.sheet(0, {range: ""}), entireSheet);
   t.same(workbook.sheet(0, {range: []}), entireSheet);
+  t.same(workbook.sheet(0, {range: []}).columns, Object.keys(entireSheet[0]));
 
   // "B2:C3"
   // [[1,1],[2,2]]
@@ -174,11 +186,6 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     {H: 37, I: 38, J: 39},
   ]);
 
-  // "2"
-  // [[,1]]
-  t.same(workbook.sheet(0, {range: "2"}), entireSheet.slice(1));
-  t.same(workbook.sheet(0, {range: [[undefined, 1]]}), entireSheet.slice(1));
-
   // ":I"
   // [,[1,]]
   const sheetJ = [
@@ -193,6 +200,16 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   // ":ZZ" (doesn't cause extra column fields)
   t.same(workbook.sheet(0, {range: ":ZZ"}), entireSheet);
 
+  // "2"
+  // [[,1]]
+  t.same(workbook.sheet(0, {range: "2"}), entireSheet.slice(1));
+  t.same(workbook.sheet(0, {range: [[undefined, 1]]}), entireSheet.slice(1));
+
+  // ":2"
+  // [[,],[,1]]
+  t.same(workbook.sheet(0, {range: ":2"}), entireSheet.slice(0, 2));
+  t.same(workbook.sheet(0, {range: [[], [undefined, 1]]}), entireSheet.slice(0, 2));
+
   t.end();
 });
 

From e7c82d48ab8fc5112e7260f85e0fdd9c6655d3c4 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 09:12:00 -0700
Subject: [PATCH 14/34] Example of .xlsx in README

---
 README.md | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 5a2387ee..e28f42ad 100644
--- a/README.md
+++ b/README.md
@@ -381,10 +381,15 @@ const db = await FileAttachment("chinook.db").sqlite();
 
 <a href="#attachment_xlsx" name="attachment_xlsx">#</a> *attachment*.<b>xlsx</b>() [<>](https://github.com/observablehq/stdlib/blob/master/src/xlsx.js "Source")
 
-Returns a promise to the file loaded as an [ExcelWorkbook](https://observablehq.com/@observablehq/excelworkbook).
+Returns a promise to the file loaded as an [ExcelWorkbook](https://observablehq.com/@observablehq/excel-workbook).
 
 <a href="#FileAttachments" name="FileAttachments">#</a> <b>FileAttachments</b>(<i>resolve</i>) [<>](https://github.com/observablehq/stdlib/blob/master/src/fileAttachment.js "Source")
 
+```js
+const workbook = await FileAttachment("profit-and-loss.xlsx").xlsx();
+const sheet = workbook.sheet("Sheet1", { range: "B4:AF234", headers: true });
+```
+
 *Note: this function is not part of the Observable standard library (in notebooks), but is provided by this module as a means for defining custom file attachment implementations when working directly with the Observable runtime.*
 
 Returns a [*FileAttachment*](#FileAttachment) function given the specified *resolve* function. The *resolve* function is an async function that takes a *name* and returns a URL at which the file of that name can be loaded. For example:

From 1440400697634b235761376970be5a3e9c70eca7 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 09:24:11 -0700
Subject: [PATCH 15/34] Remove Excel from Workbook naming

---
 README.md             |  2 +-
 src/fileAttachment.js |  4 ++--
 src/xlsx.js           |  4 ++--
 test/xlsx-test.js     | 20 ++++++++++----------
 4 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/README.md b/README.md
index e28f42ad..d70c091c 100644
--- a/README.md
+++ b/README.md
@@ -381,7 +381,7 @@ const db = await FileAttachment("chinook.db").sqlite();
 
 <a href="#attachment_xlsx" name="attachment_xlsx">#</a> *attachment*.<b>xlsx</b>() [<>](https://github.com/observablehq/stdlib/blob/master/src/xlsx.js "Source")
 
-Returns a promise to the file loaded as an [ExcelWorkbook](https://observablehq.com/@observablehq/excel-workbook).
+Returns a promise to the file loaded as a [Workbook](https://observablehq.com/@observablehq/xlsx-workbook).
 
 <a href="#FileAttachments" name="FileAttachments">#</a> <b>FileAttachments</b>(<i>resolve</i>) [<>](https://github.com/observablehq/stdlib/blob/master/src/fileAttachment.js "Source")
 
diff --git a/src/fileAttachment.js b/src/fileAttachment.js
index d185dded..90d0d03e 100644
--- a/src/fileAttachment.js
+++ b/src/fileAttachment.js
@@ -2,7 +2,7 @@ import {autoType, csvParse, csvParseRows, tsvParse, tsvParseRows} from "d3-dsv";
 import {require as requireDefault} from "d3-require";
 import {arrow, jszip, exceljs} from "./dependencies.js";
 import {SQLiteDatabaseClient} from "./sqlite.js";
-import {ExcelWorkbook} from "./xlsx.js";
+import {Workbook} from "./xlsx.js";
 
 async function remote_fetch(file) {
   const response = await fetch(await file.url());
@@ -73,7 +73,7 @@ class AbstractFile {
   }
   async xlsx() {
     const [ExcelJS, buffer] = await Promise.all([requireDefault(exceljs.resolve()), this.arrayBuffer()]);
-    return new ExcelWorkbook(await new ExcelJS.Workbook().xlsx.load(buffer));
+    return new Workbook(await new ExcelJS.Workbook().xlsx.load(buffer));
   }
 }
 
diff --git a/src/xlsx.js b/src/xlsx.js
index 7acf0ce9..0fdcb34f 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -1,4 +1,4 @@
-export class ExcelWorkbook {
+export class Workbook {
   constructor(workbook) {
     Object.defineProperty(this, "_", {value: workbook});
     this.sheetNames = this._.worksheets.map((sheet) => sheet.name);
@@ -50,7 +50,7 @@ function valueOf(cell) {
     if (value.richText) return value.richText.map((d) => d.text).join("");
     if (value.text)
       return value.hyperlink
-        ? `<a href="${value.hyperlink}">${value.text}</a>`
+        ? `<a href="${encodeURI(value.hyperlink)}">${value.text.replace(/</g, "&lt;")}</a>`
         : value.text;
     return "";
   }
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 85902da7..ecd48b1e 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -1,5 +1,5 @@
 import {test} from "tap";
-import {ExcelWorkbook} from "../src/xlsx.js";
+import {Workbook} from "../src/xlsx.js";
 
 function mockWorkbook(contents, overrides = {}) {
   return {
@@ -19,19 +19,19 @@ function mockWorkbook(contents, overrides = {}) {
 }
 
 test("FileAttachment.xlsx reads sheet names", (t) => {
-  const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
+  const workbook = new Workbook(mockWorkbook({Sheet1: []}));
   t.same(workbook.sheetNames, ["Sheet1"]);
   t.end();
 });
 
 test("FileAttachment.xlsx sheet(name) throws on unknown sheet name", (t) => {
-  const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
+  const workbook = new Workbook(mockWorkbook({Sheet1: []}));
   t.throws(() => workbook.sheet("bad"));
   t.end();
 });
 
 test("FileAttachment.xlsx reads sheets", (t) => {
-  const workbook = new ExcelWorkbook(
+  const workbook = new Workbook(
     mockWorkbook({
       Sheet1: [
         ["one", "two", "three"],
@@ -51,7 +51,7 @@ test("FileAttachment.xlsx reads sheets", (t) => {
 });
 
 test("FileAttachment.xlsx reads sheets with different types", (t) => {
-  const workbook = new ExcelWorkbook(
+  const workbook = new Workbook(
     mockWorkbook({
       Sheet1: [
         ["one", null, {richText: [{text: "two"}, {text: "three"}]}, undefined],
@@ -76,7 +76,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
 });
 
 test("FileAttachment.xlsx reads sheets with headers", (t) => {
-  const workbook = new ExcelWorkbook(
+  const workbook = new Workbook(
     mockWorkbook({
       Sheet1: [
         [null, "one", "one", "two", "A"],
@@ -101,7 +101,7 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
 });
 
 test("FileAttachment.xlsx reads sheet ranges", (t) => {
-  const workbook = new ExcelWorkbook(
+  const workbook = new Workbook(
     mockWorkbook({
       Sheet1: [
         [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
@@ -214,14 +214,14 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
 });
 
 test("FileAttachment.xlsx throws on unknown range specifier", (t) => {
-  const workbook = new ExcelWorkbook(mockWorkbook({Sheet1: []}));
+  const workbook = new Workbook(mockWorkbook({Sheet1: []}));
   t.throws(() => workbook.sheet(0, {range: 0}));
   t.end();
 });
 
 test("FileAttachment.xlsx derives column names such as A AA AAA…", (t) => {
   const l0 = 26 * 26 * 26 + 26 * 26 + 26;
-  const workbook = new ExcelWorkbook(
+  const workbook = new Workbook(
     mockWorkbook({
       Sheet1: [Array.from({length: l0}).fill(1)],
     })
@@ -230,7 +230,7 @@ test("FileAttachment.xlsx derives column names such as A AA AAA…", (t) => {
     workbook.sheet(0, {headers: false}).columns.filter((d) => d.match(/^A*$/)),
     ["A", "AA", "AAA"]
   );
-  const workbook1 = new ExcelWorkbook(
+  const workbook1 = new Workbook(
     mockWorkbook({
       Sheet1: [Array.from({length: l0 + 1}).fill(1)],
     })

From d444ebec69e9c230d8aaaa1ed15f5610e0166e2b Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 13:10:56 -0700
Subject: [PATCH 16/34] Fix dates

---
 src/xlsx.js       |  2 +-
 test/xlsx-test.js | 35 +++++++++++++++++++++--------------
 2 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 0fdcb34f..43b658c1 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -52,7 +52,7 @@ function valueOf(cell) {
       return value.hyperlink
         ? `<a href="${encodeURI(value.hyperlink)}">${value.text.replace(/</g, "&lt;")}</a>`
         : value.text;
-    return "";
+    return value;
   }
   return value;
 }
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index ecd48b1e..0a9f8781 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -6,14 +6,17 @@ function mockWorkbook(contents, overrides = {}) {
     worksheets: Object.keys(contents).map((name) => ({name})),
     getWorksheet(name) {
       const _rows = contents[name];
-      return Object.assign({
-        _rows: _rows.map((row) => ({
-          _cells: row.map((cell) => ({value: cell})),
-          hasValues: !!row.length,
-        })),
-        rowCount: _rows.length,
-        columnCount: Math.max(..._rows.map((r) => r.length)),
-      }, overrides);
+      return Object.assign(
+        {
+          _rows: _rows.map((row) => ({
+            _cells: row.map((cell) => ({value: cell})),
+            hasValues: !!row.length,
+          })),
+          rowCount: _rows.length,
+          columnCount: Math.max(..._rows.map((r) => r.length)),
+        },
+        overrides
+      );
     },
   };
 }
@@ -61,7 +64,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
           2,
           {formula: "=B2*5", result: 10},
         ],
-        [ {/* empty object */} ],
+        [{}, new Date(Date.UTC(2020, 0, 1))],
         [],
       ],
     })
@@ -69,7 +72,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
   t.same(workbook.sheet(0), [
     {A: "one", C: "twothree"},
     {A: "plain text", B: `<a href="https://example.com">link</a>`, C: 2, D: 10},
-    {A: ""},
+    {A: {}, B: new Date(Date.UTC(2020, 0, 1))},
     {},
   ]);
   t.end();
@@ -79,15 +82,15 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
   const workbook = new Workbook(
     mockWorkbook({
       Sheet1: [
-        [null, "one", "one", "two", "A"],
-        [1, null, 3, 4, 5],
+        [null, "one", "one", "two", "A", "0"],
+        [1, null, 3, 4, 5, "zero"],
         [6, 7, 8, 9, 10],
       ],
     })
     // }, { columnCount: 10 })
   );
   t.same(workbook.sheet(0, {headers: true}), [
-    {A: 1, one_: 3, two: 4, A_: 5},
+    {A: 1, one_: 3, two: 4, A_: 5, 0: "zero"},
     {A: 6, one: 7, one_: 8, two: 9, A_: 10},
   ]);
   t.same(workbook.sheet(0, {headers: true}).columns, [
@@ -96,6 +99,7 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
     "one_",
     "two",
     "A_",
+    "0",
   ]);
   t.end();
 });
@@ -208,7 +212,10 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   // ":2"
   // [[,],[,1]]
   t.same(workbook.sheet(0, {range: ":2"}), entireSheet.slice(0, 2));
-  t.same(workbook.sheet(0, {range: [[], [undefined, 1]]}), entireSheet.slice(0, 2));
+  t.same(
+    workbook.sheet(0, {range: [[], [undefined, 1]]}),
+    entireSheet.slice(0, 2)
+  );
 
   t.end();
 });

From 410f4c9250b06decefac3ebd2049ba8ec165e4b1 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Thu, 9 Sep 2021 16:47:20 -0700
Subject: [PATCH 17/34] Fix for sharedFormula

---
 src/xlsx.js       | 14 ++++++++------
 test/xlsx-test.js |  9 ++++++++-
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 43b658c1..9e880169 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -45,12 +45,16 @@ function extract(sheet, {range, headers}) {
 function valueOf(cell) {
   if (!cell) return;
   const {value} = cell;
+  if (value && value instanceof Date) return value;
   if (value && typeof value === "object") {
-    if (value.formula) return value.result;
+    if (value.formula || value.sharedFormula) return value.result;
     if (value.richText) return value.richText.map((d) => d.text).join("");
     if (value.text)
       return value.hyperlink
-        ? `<a href="${encodeURI(value.hyperlink)}">${value.text.replace(/</g, "&lt;")}</a>`
+        ? `<a href="${encodeURI(value.hyperlink)}">${value.text.replace(
+            /</g,
+            "&lt;"
+          )}</a>`
         : value.text;
     return value;
   }
@@ -59,10 +63,8 @@ function valueOf(cell) {
 
 function parseRange(specifier = [], {columnCount, rowCount}) {
   if (typeof specifier === "string") {
-    const [
-      [c0 = 0, r0 = 0],
-      [c1 = columnCount - 1, r1 = rowCount - 1] = [],
-    ] = specifier.split(":").map(NN);
+    const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1] = []] =
+      specifier.split(":").map(NN);
     return [
       [c0, r0],
       [c1, r1],
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 0a9f8781..ed150b03 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -63,6 +63,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
           {text: "link", hyperlink: "https://example.com"},
           2,
           {formula: "=B2*5", result: 10},
+          {sharedFormula: "=B2*6", result: 12},
         ],
         [{}, new Date(Date.UTC(2020, 0, 1))],
         [],
@@ -71,7 +72,13 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
   );
   t.same(workbook.sheet(0), [
     {A: "one", C: "twothree"},
-    {A: "plain text", B: `<a href="https://example.com">link</a>`, C: 2, D: 10},
+    {
+      A: "plain text",
+      B: `<a href="https://example.com">link</a>`,
+      C: 2,
+      D: 10,
+      E: 12,
+    },
     {A: {}, B: new Date(Date.UTC(2020, 0, 1))},
     {},
   ]);

From 57cb0e0cd80d89a7c21c85dece74a5bd014b877d Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 10 Sep 2021 09:53:00 -0700
Subject: [PATCH 18/34] Coerce errors to NaN

---
 src/xlsx.js       | 3 ++-
 test/xlsx-test.js | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 9e880169..8747e57a 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -47,7 +47,8 @@ function valueOf(cell) {
   const {value} = cell;
   if (value && value instanceof Date) return value;
   if (value && typeof value === "object") {
-    if (value.formula || value.sharedFormula) return value.result;
+    if (value.formula || value.sharedFormula)
+      return value.result && value.result.error ? NaN : value.result;
     if (value.richText) return value.richText.map((d) => d.text).join("");
     if (value.text)
       return value.hyperlink
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index ed150b03..6dc0a966 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -64,6 +64,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
           2,
           {formula: "=B2*5", result: 10},
           {sharedFormula: "=B2*6", result: 12},
+          {sharedFormula: "=Z2*6", result: {error: "#REF!"}},
         ],
         [{}, new Date(Date.UTC(2020, 0, 1))],
         [],
@@ -78,6 +79,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
       C: 2,
       D: 10,
       E: 12,
+      F: NaN,
     },
     {A: {}, B: new Date(Date.UTC(2020, 0, 1))},
     {},

From e2976b190c8452b428bf922368bc5f02cfc517c6 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 10 Sep 2021 10:09:59 -0700
Subject: [PATCH 19/34] Properly escape html

---
 src/xlsx.js       | 22 +++++++++++++++++++---
 test/xlsx-test.js |  5 ++---
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 8747e57a..a2ddc612 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -52,9 +52,8 @@ function valueOf(cell) {
     if (value.richText) return value.richText.map((d) => d.text).join("");
     if (value.text)
       return value.hyperlink
-        ? `<a href="${encodeURI(value.hyperlink)}">${value.text.replace(
-            /</g,
-            "&lt;"
+        ? `<a href="${encodeURI(value.hyperlink)}">${escapeHTML(
+            value.text
           )}</a>`
         : value.text;
     return value;
@@ -62,6 +61,23 @@ function valueOf(cell) {
   return value;
 }
 
+function escapeHTML(string) {
+  return string.replace(/[&<>"']/g, (m) => {
+    switch (m) {
+      case "&":
+        return "&amp;";
+      case "<":
+        return "&lt;";
+      case ">":
+        return "&gt;";
+      case '"':
+        return "&quot;";
+      case "'":
+        return "&#39;";
+    }
+  });
+}
+
 function parseRange(specifier = [], {columnCount, rowCount}) {
   if (typeof specifier === "string") {
     const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1] = []] =
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 6dc0a966..7914229d 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -60,7 +60,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
         ["one", null, {richText: [{text: "two"}, {text: "three"}]}, undefined],
         [
           {text: "plain text"},
-          {text: "link", hyperlink: "https://example.com"},
+          {text: `link&</a>"'?`, hyperlink: 'https://example.com?q="'},
           2,
           {formula: "=B2*5", result: 10},
           {sharedFormula: "=B2*6", result: 12},
@@ -75,7 +75,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
     {A: "one", C: "twothree"},
     {
       A: "plain text",
-      B: `<a href="https://example.com">link</a>`,
+      B: `<a href="https://example.com?q=%22">link&amp;&lt;/a&gt;&quot;&#39;?</a>`,
       C: 2,
       D: 10,
       E: 12,
@@ -96,7 +96,6 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
         [6, 7, 8, 9, 10],
       ],
     })
-    // }, { columnCount: 10 })
   );
   t.same(workbook.sheet(0, {headers: true}), [
     {A: 1, one_: 3, two: 4, A_: 5, 0: "zero"},

From b97b9f6c7f2e26d88307974db27629b38ff81526 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 10 Sep 2021 10:25:15 -0700
Subject: [PATCH 20/34] Make sheetNames read-only

---
 src/xlsx.js | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index a2ddc612..1704a22c 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -1,7 +1,13 @@
 export class Workbook {
   constructor(workbook) {
-    Object.defineProperty(this, "_", {value: workbook});
-    this.sheetNames = this._.worksheets.map((sheet) => sheet.name);
+    Object.defineProperties(this, {
+      _: {value: workbook},
+      sheetNames: {
+        value: workbook.worksheets.map((sheet) => sheet.name),
+        writable: false,
+        enumerable: true,
+      },
+    });
   }
   sheet(name, {range, headers = false} = {}) {
     const sname =

From e5eb8d6339180ac433dde343a2cabeea350181fc Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 10 Sep 2021 14:23:38 -0700
Subject: [PATCH 21/34] Require colons in range specifiers

---
 src/xlsx.js       |  5 +++--
 test/xlsx-test.js | 55 +++++++++++++++++++++++++----------------------
 2 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 1704a22c..d9a747c7 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -86,7 +86,8 @@ function escapeHTML(string) {
 
 function parseRange(specifier = [], {columnCount, rowCount}) {
   if (typeof specifier === "string") {
-    const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1] = []] =
+    if (!specifier.includes(":")) throw new Error("Malformed range specifier");
+    const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1]] =
       specifier.split(":").map(NN);
     return [
       [c0, r0],
@@ -102,7 +103,7 @@ function parseRange(specifier = [], {columnCount, rowCount}) {
       [c1, r1],
     ];
   } else {
-    throw new Error(`Unknown range specifier`);
+    throw new Error("Unknown range specifier");
   }
 }
 
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 7914229d..a90b2454 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -124,8 +124,11 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     })
   );
 
-  // undefined
   // ""
+  t.throws(() => t.same(workbook.sheet(0, {range: ""}), entireSheet));
+
+  // undefined
+  // ":"
   // []
   const entireSheet = [
     {A: 0, B: 1, C: 2, D: 3, E: 4, F: 5, G: 6, H: 7, I: 8, J: 9},
@@ -134,7 +137,7 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     {A: 30, B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
   ];
   t.same(workbook.sheet(0), entireSheet);
-  t.same(workbook.sheet(0, {range: ""}), entireSheet);
+  t.same(workbook.sheet(0, {range: ":"}), entireSheet);
   t.same(workbook.sheet(0, {range: []}), entireSheet);
   t.same(workbook.sheet(0, {range: []}).columns, Object.keys(entireSheet[0]));
 
@@ -170,9 +173,9 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     {A: 20, B: 21, C: 22},
   ]);
 
-  // "B2"
+  // "B2:"
   // [[1,1]]
-  t.same(workbook.sheet(0, {range: "B2"}), [
+  t.same(workbook.sheet(0, {range: "B2:"}), [
     {B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
     {B: 21, C: 22, D: 23, E: 24, F: 25, G: 26, H: 27, I: 28, J: 29},
     {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
@@ -183,38 +186,38 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
   ]);
 
-  // "H"
+  // "H:"
   // [[7]]
-  t.same(workbook.sheet(0, {range: "H"}), [
-    {H: 7, I: 8, J: 9},
-    {H: 17, I: 18, J: 19},
-    {H: 27, I: 28, J: 29},
-    {H: 37, I: 38, J: 39},
-  ]);
-  t.same(workbook.sheet(0, {range: [[7]]}), [
+  const sheetH = [
     {H: 7, I: 8, J: 9},
     {H: 17, I: 18, J: 19},
     {H: 27, I: 28, J: 29},
     {H: 37, I: 38, J: 39},
-  ]);
+  ];
+  t.same(workbook.sheet(0, {range: "H:"}), sheetH);
+  t.same(workbook.sheet(0, {range: [[7]]}), sheetH);
 
-  // ":I"
-  // [,[1,]]
-  const sheetJ = [
-    {I: 8, J: 9},
-    {I: 18, J: 19},
-    {I: 28, J: 29},
-    {I: 38, J: 39},
+  // ":C"
+  // [,[,2]]
+  const sheetC = [
+    {A: 0, B: 1, C: 2},
+    {A: 10, B: 11, C: 12},
+    {A: 20, B: 21, C: 22},
+    {A: 30, B: 31, C: 32},
   ];
-  t.same(workbook.sheet(0, {range: "I"}), sheetJ);
-  t.same(workbook.sheet(0, {range: [[8, undefined], undefined]}), sheetJ);
+  t.same(workbook.sheet(0, {range: ":C"}), sheetC);
+  t.same(workbook.sheet(0, {range: [undefined, [2]]}), sheetC);
 
-  // ":ZZ" (doesn't cause extra column fields)
-  t.same(workbook.sheet(0, {range: ":ZZ"}), entireSheet);
+  // ":Z"
+  t.same(workbook.sheet(0, {range: ":Z"}), entireSheet);
+  t.same(
+    workbook.sheet(0, {range: ":Z"}).columns,
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("")
+  );
 
-  // "2"
+  // "2:"
   // [[,1]]
-  t.same(workbook.sheet(0, {range: "2"}), entireSheet.slice(1));
+  t.same(workbook.sheet(0, {range: "2:"}), entireSheet.slice(1));
   t.same(workbook.sheet(0, {range: [[undefined, 1]]}), entireSheet.slice(1));
 
   // ":2"

From 81433c66ef84db1fc750abce529ddc7fa0c68948 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Fri, 10 Sep 2021 15:27:27 -0700
Subject: [PATCH 22/34] Include row numbers

---
 src/xlsx.js       | 20 +++++++++++---------
 test/xlsx-test.js |  8 ++++++--
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index d9a747c7..96a27561 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -25,7 +25,7 @@ export class Workbook {
 function extract(sheet, {range, headers}) {
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
   const headerRow = headers && sheet._rows[r0++];
-  let names = new Set();
+  let names = new Set(["#"]);
   for (let n = c0; n <= c1; n++) {
     let name = (headerRow ? valueOf(headerRow._cells[n]) : null) || AA(n);
     while (names.has(name)) name += "_";
@@ -33,18 +33,20 @@ function extract(sheet, {range, headers}) {
   }
   names = new Array(c0).concat(Array.from(names));
 
-  const output = new Array(r1 - r0 + 1).fill({});
+  const output = new Array(r1 - r0 + 1);
   for (let r = r0; r <= r1; r++) {
+    const row = (output[r - r0] = Object.defineProperty({}, "#", {
+      value: r + 1,
+    }));
     const _row = sheet._rows[r];
-    if (!_row || !_row.hasValues) continue;
-    const row = (output[r - r0] = {});
-    for (let c = c0; c <= c1; c++) {
-      const value = valueOf(_row._cells[c]);
-      if (value != null) row[names[c]] = value;
-    }
+    if (_row && _row.hasValues)
+      for (let c = c0; c <= c1; c++) {
+        const value = valueOf(_row._cells[c]);
+        if (value != null) row[names[c + 1]] = value;
+      }
   }
 
-  output.columns = names.filter(() => true);
+  output.columns = names.filter(() => true); // Filter sparse columns
   return output;
 }
 
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index a90b2454..610ed609 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -102,6 +102,7 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
     {A: 6, one: 7, one_: 8, two: 9, A_: 10},
   ]);
   t.same(workbook.sheet(0, {headers: true}).columns, [
+    "#",
     "A",
     "one",
     "one_",
@@ -139,7 +140,10 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   t.same(workbook.sheet(0), entireSheet);
   t.same(workbook.sheet(0, {range: ":"}), entireSheet);
   t.same(workbook.sheet(0, {range: []}), entireSheet);
-  t.same(workbook.sheet(0, {range: []}).columns, Object.keys(entireSheet[0]));
+  t.same(workbook.sheet(0, {range: []}).columns, [
+    "#",
+    ...Object.keys(entireSheet[0]),
+  ]);
 
   // "B2:C3"
   // [[1,1],[2,2]]
@@ -212,7 +216,7 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   t.same(workbook.sheet(0, {range: ":Z"}), entireSheet);
   t.same(
     workbook.sheet(0, {range: ":Z"}).columns,
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("")
+    "#ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("")
   );
 
   // "2:"

From 2f26284140ebbb40737defbb6aa6aa9de7789ee1 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Sat, 11 Sep 2021 17:32:29 -0700
Subject: [PATCH 23/34] Use only string form ranges

---
 src/xlsx.js       | 31 +++++++++------------------
 test/xlsx-test.js | 53 +++++------------------------------------------
 2 files changed, 15 insertions(+), 69 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 96a27561..df128fd4 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -86,27 +86,16 @@ function escapeHTML(string) {
   });
 }
 
-function parseRange(specifier = [], {columnCount, rowCount}) {
-  if (typeof specifier === "string") {
-    if (!specifier.includes(":")) throw new Error("Malformed range specifier");
-    const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1]] =
-      specifier.split(":").map(NN);
-    return [
-      [c0, r0],
-      [c1, r1],
-    ];
-  } else if (typeof specifier === "object") {
-    const [
-      [c0 = 0, r0 = 0] = [],
-      [c1 = columnCount - 1, r1 = rowCount - 1] = [],
-    ] = specifier;
-    return [
-      [c0, r0],
-      [c1, r1],
-    ];
-  } else {
-    throw new Error("Unknown range specifier");
-  }
+function parseRange(specifier = ":", {columnCount, rowCount}) {
+  if (typeof specifier !== "string") throw new Error("Unknown range specifier");
+  if (!specifier.match(/^[A-Z]*[0-9]*:[A-Z]*[0-9]*$/))
+    throw new Error("Malformed range specifier");
+  const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1]] =
+    specifier.split(":").map(NN);
+  return [
+    [c0, r0],
+    [c1, r1],
+  ];
 }
 
 function AA(c) {
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 610ed609..ca1f61e7 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -130,7 +130,6 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
 
   // undefined
   // ":"
-  // []
   const entireSheet = [
     {A: 0, B: 1, C: 2, D: 3, E: 4, F: 5, G: 6, H: 7, I: 8, J: 9},
     {A: 10, B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
@@ -139,78 +138,43 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   ];
   t.same(workbook.sheet(0), entireSheet);
   t.same(workbook.sheet(0, {range: ":"}), entireSheet);
-  t.same(workbook.sheet(0, {range: []}), entireSheet);
-  t.same(workbook.sheet(0, {range: []}).columns, [
-    "#",
-    ...Object.keys(entireSheet[0]),
-  ]);
+  t.same(workbook.sheet(0).columns, ["#", ...Object.keys(entireSheet[0])]);
 
   // "B2:C3"
-  // [[1,1],[2,2]]
   t.same(workbook.sheet(0, {range: "B2:C3"}), [
     {B: 11, C: 12},
     {B: 21, C: 22},
   ]);
-  t.same(
-    workbook.sheet(0, {
-      range: [
-        [1, 1],
-        [2, 2],
-      ],
-    }),
-    [
-      {B: 11, C: 12},
-      {B: 21, C: 22},
-    ]
-  );
 
   // ":C3"
-  // [,[2,2]]
   t.same(workbook.sheet(0, {range: ":C3"}), [
     {A: 0, B: 1, C: 2},
     {A: 10, B: 11, C: 12},
     {A: 20, B: 21, C: 22},
   ]);
-  t.same(workbook.sheet(0, {range: [undefined, [2, 2]]}), [
-    {A: 0, B: 1, C: 2},
-    {A: 10, B: 11, C: 12},
-    {A: 20, B: 21, C: 22},
-  ]);
 
   // "B2:"
-  // [[1,1]]
   t.same(workbook.sheet(0, {range: "B2:"}), [
     {B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
     {B: 21, C: 22, D: 23, E: 24, F: 25, G: 26, H: 27, I: 28, J: 29},
     {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
   ]);
-  t.same(workbook.sheet(0, {range: [[1, 1]]}), [
-    {B: 11, C: 12, D: 13, E: 14, F: 15, G: 16, H: 17, I: 18, J: 19},
-    {B: 21, C: 22, D: 23, E: 24, F: 25, G: 26, H: 27, I: 28, J: 29},
-    {B: 31, C: 32, D: 33, E: 34, F: 35, G: 36, H: 37, I: 38, J: 39},
-  ]);
 
   // "H:"
-  // [[7]]
-  const sheetH = [
+  t.same(workbook.sheet(0, {range: "H:"}), [
     {H: 7, I: 8, J: 9},
     {H: 17, I: 18, J: 19},
     {H: 27, I: 28, J: 29},
     {H: 37, I: 38, J: 39},
-  ];
-  t.same(workbook.sheet(0, {range: "H:"}), sheetH);
-  t.same(workbook.sheet(0, {range: [[7]]}), sheetH);
+  ]);
 
   // ":C"
-  // [,[,2]]
-  const sheetC = [
+  t.same(workbook.sheet(0, {range: ":C"}), [
     {A: 0, B: 1, C: 2},
     {A: 10, B: 11, C: 12},
     {A: 20, B: 21, C: 22},
     {A: 30, B: 31, C: 32},
-  ];
-  t.same(workbook.sheet(0, {range: ":C"}), sheetC);
-  t.same(workbook.sheet(0, {range: [undefined, [2]]}), sheetC);
+  ]);
 
   // ":Z"
   t.same(workbook.sheet(0, {range: ":Z"}), entireSheet);
@@ -220,17 +184,10 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
   );
 
   // "2:"
-  // [[,1]]
   t.same(workbook.sheet(0, {range: "2:"}), entireSheet.slice(1));
-  t.same(workbook.sheet(0, {range: [[undefined, 1]]}), entireSheet.slice(1));
 
   // ":2"
-  // [[,],[,1]]
   t.same(workbook.sheet(0, {range: ":2"}), entireSheet.slice(0, 2));
-  t.same(
-    workbook.sheet(0, {range: [[], [undefined, 1]]}),
-    entireSheet.slice(0, 2)
-  );
 
   t.end();
 });

From 66a539cd32485c93ac9540eb9fb9ab89436cc61f Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Sat, 11 Sep 2021 17:34:19 -0700
Subject: [PATCH 24/34] Coerce range specifiers to strings

---
 src/xlsx.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index df128fd4..8ea3ba90 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -87,7 +87,7 @@ function escapeHTML(string) {
 }
 
 function parseRange(specifier = ":", {columnCount, rowCount}) {
-  if (typeof specifier !== "string") throw new Error("Unknown range specifier");
+  specifier += "";
   if (!specifier.match(/^[A-Z]*[0-9]*:[A-Z]*[0-9]*$/))
     throw new Error("Malformed range specifier");
   const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1]] =

From fcb6eb7798744605b16d6cae05f5e6e79b846e22 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Mon, 13 Sep 2021 16:19:57 -0700
Subject: [PATCH 25/34] Update README.md

Co-authored-by: Mike Bostock <mbostock@gmail.com>
---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 8d02e353..e0b83e75 100644
--- a/README.md
+++ b/README.md
@@ -385,7 +385,7 @@ Returns a promise to the file loaded as a [Workbook](https://observablehq.com/@o
 
 ```js
 const workbook = await FileAttachment("profit-and-loss.xlsx").xlsx();
-const sheet = workbook.sheet("Sheet1", { range: "B4:AF234", headers: true });
+const sheet = workbook.sheet("Sheet1", {range: "B4:AF234", headers: true});
 ```
 
 <a href="#attachment_xml" name="attachment_xml">#</a> *attachment*.<b>xml</b>() [<>](https://github.com/observablehq/stdlib/blob/master/src/fileAttachment.js "Source")

From 162d55e5d2e07aab3a7df5083205e15b1323f526 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Mon, 13 Sep 2021 16:24:09 -0700
Subject: [PATCH 26/34] Apply suggestions from code review

Co-authored-by: Mike Bostock <mbostock@gmail.com>
---
 README.md   |  2 +-
 src/xlsx.js | 10 +++-------
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index e0b83e75..ae8b1eea 100644
--- a/README.md
+++ b/README.md
@@ -381,7 +381,7 @@ const db = await FileAttachment("chinook.db").sqlite();
 
 <a href="#attachment_xlsx" name="attachment_xlsx">#</a> *attachment*.<b>xlsx</b>() [<>](https://github.com/observablehq/stdlib/blob/master/src/xlsx.js "Source")
 
-Returns a promise to the file loaded as a [Workbook](https://observablehq.com/@observablehq/xlsx-workbook).
+Returns a promise to the file loaded as a [Workbook](https://observablehq.com/@observablehq/xlsx).
 
 ```js
 const workbook = await FileAttachment("profit-and-loss.xlsx").xlsx();
diff --git a/src/xlsx.js b/src/xlsx.js
index 8ea3ba90..630a5f95 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -2,19 +2,15 @@ export class Workbook {
   constructor(workbook) {
     Object.defineProperties(this, {
       _: {value: workbook},
-      sheetNames: {
-        value: workbook.worksheets.map((sheet) => sheet.name),
-        writable: false,
-        enumerable: true,
-      },
+      sheetNames: {value: workbook.worksheets.map(s => s.name), enumerable: true}
     });
   }
   sheet(name, {range, headers = false} = {}) {
     const sname =
       typeof name === "number"
         ? this.sheetNames[name]
-        : this.sheetNames.includes(name + "")
-        ? name + ""
+        : this.sheetNames.includes(name += "")
+        ? name
         : null;
     if (sname == null) throw new Error(`Sheet not found: ${name}`);
     const sheet = this._.getWorksheet(sname);

From 9c9e91ba6c69e7edbfb1b5807163035295971d4f Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 09:59:48 -0700
Subject: [PATCH 27/34] Simplify hyperlinks

---
 src/xlsx.js       | 23 ++---------------------
 test/xlsx-test.js |  2 +-
 2 files changed, 3 insertions(+), 22 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 630a5f95..3156577e 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -55,33 +55,14 @@ function valueOf(cell) {
       return value.result && value.result.error ? NaN : value.result;
     if (value.richText) return value.richText.map((d) => d.text).join("");
     if (value.text)
-      return value.hyperlink
-        ? `<a href="${encodeURI(value.hyperlink)}">${escapeHTML(
-            value.text
-          )}</a>`
+      return value.hyperlink && value.hyperlink !== value.text
+        ? `${value.hyperlink} ${value.text}`
         : value.text;
     return value;
   }
   return value;
 }
 
-function escapeHTML(string) {
-  return string.replace(/[&<>"']/g, (m) => {
-    switch (m) {
-      case "&":
-        return "&amp;";
-      case "<":
-        return "&lt;";
-      case ">":
-        return "&gt;";
-      case '"':
-        return "&quot;";
-      case "'":
-        return "&#39;";
-    }
-  });
-}
-
 function parseRange(specifier = ":", {columnCount, rowCount}) {
   specifier += "";
   if (!specifier.match(/^[A-Z]*[0-9]*:[A-Z]*[0-9]*$/))
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index ca1f61e7..7e7ee868 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -75,7 +75,7 @@ test("FileAttachment.xlsx reads sheets with different types", (t) => {
     {A: "one", C: "twothree"},
     {
       A: "plain text",
-      B: `<a href="https://example.com?q=%22">link&amp;&lt;/a&gt;&quot;&#39;?</a>`,
+      B: `https://example.com?q=" link&</a>"'?`,
       C: 2,
       D: 10,
       E: 12,

From 1a0345ebd5d272c7fd8af9a6e041b04e53144f5a Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 10:01:56 -0700
Subject: [PATCH 28/34] Prettier

---
 src/xlsx.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 3156577e..8ca653b9 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -2,14 +2,17 @@ export class Workbook {
   constructor(workbook) {
     Object.defineProperties(this, {
       _: {value: workbook},
-      sheetNames: {value: workbook.worksheets.map(s => s.name), enumerable: true}
+      sheetNames: {
+        value: workbook.worksheets.map((s) => s.name),
+        enumerable: true,
+      },
     });
   }
   sheet(name, {range, headers = false} = {}) {
     const sname =
       typeof name === "number"
         ? this.sheetNames[name]
-        : this.sheetNames.includes(name += "")
+        : this.sheetNames.includes((name += ""))
         ? name
         : null;
     if (sname == null) throw new Error(`Sheet not found: ${name}`);

From 5daef26a2be1563e359729fadb54ff8e46220f5e Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 10:03:25 -0700
Subject: [PATCH 29/34] Pass options through

---
 src/xlsx.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 8ca653b9..b36b15ee 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -8,7 +8,7 @@ export class Workbook {
       },
     });
   }
-  sheet(name, {range, headers = false} = {}) {
+  sheet(name, options) {
     const sname =
       typeof name === "number"
         ? this.sheetNames[name]
@@ -17,11 +17,11 @@ export class Workbook {
         : null;
     if (sname == null) throw new Error(`Sheet not found: ${name}`);
     const sheet = this._.getWorksheet(sname);
-    return extract(sheet, {range, headers});
+    return extract(sheet, options);
   }
 }
 
-function extract(sheet, {range, headers}) {
+function extract(sheet, {range, headers = false} = {}) {
   let [[c0, r0], [c1, r1]] = parseRange(range, sheet);
   const headerRow = headers && sheet._rows[r0++];
   let names = new Set(["#"]);

From 92c4af1d9c737ac9dae1dad59594f8fb5409d13a Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 10:34:49 -0700
Subject: [PATCH 30/34] Rename helper functions for clarity, range tests

---
 src/xlsx.js       | 12 ++++++++----
 test/xlsx-test.js | 20 +++++++++++++++++---
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index b36b15ee..d9b81137 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -26,7 +26,7 @@ function extract(sheet, {range, headers = false} = {}) {
   const headerRow = headers && sheet._rows[r0++];
   let names = new Set(["#"]);
   for (let n = c0; n <= c1; n++) {
-    let name = (headerRow ? valueOf(headerRow._cells[n]) : null) || AA(n);
+    let name = (headerRow ? valueOf(headerRow._cells[n]) : null) || toColumn(n);
     while (names.has(name)) name += "_";
     names.add(name);
   }
@@ -71,14 +71,16 @@ function parseRange(specifier = ":", {columnCount, rowCount}) {
   if (!specifier.match(/^[A-Z]*[0-9]*:[A-Z]*[0-9]*$/))
     throw new Error("Malformed range specifier");
   const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1]] =
-    specifier.split(":").map(NN);
+    specifier.split(":").map(fromCellReference);
   return [
     [c0, r0],
     [c1, r1],
   ];
 }
 
-function AA(c) {
+// Returns the default column name for a zero-based column index.
+// For example: 0 => A, 1 => B, 25 => Z, 26 => AA, 27 => AB.
+function toColumn(c) {
   let sc = "";
   c++;
   do {
@@ -87,7 +89,9 @@ function AA(c) {
   return sc;
 }
 
-function NN(s) {
+// Returns the zero-based indexes from a cell reference.
+// For example: "A1" -> [0, 0], "B2" -> [1, 1], "AA10" -> [26, 9].
+function fromCellReference(s) {
   const [, sc, sr] = s.match(/^([A-Z]*)(\d*)$/i);
   let c = undefined;
   if (sc) {
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 7e7ee868..62a36cc7 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -113,6 +113,23 @@ test("FileAttachment.xlsx reads sheets with headers", (t) => {
   t.end();
 });
 
+test("FileAttachment.xlsx throws on invalid ranges", (t) => {
+  const workbook = new Workbook(mockWorkbook({Sheet1: []}));
+  const malformed = new Error("Malformed range specifier");
+
+  t.throws(() => t.same(workbook.sheet(0, {range: ""})), malformed);
+  t.throws(() => t.same(workbook.sheet(0, {range: "-:"})), malformed);
+  t.throws(() => t.same(workbook.sheet(0, {range: " :"})), malformed);
+  t.throws(
+    () => t.same(workbook.sheet(0, {range: "a1:"})),
+    malformed,
+    "lowercase"
+  );
+  t.throws(() => t.same(workbook.sheet(0, {range: "1A:"})), malformed);
+
+  t.end();
+});
+
 test("FileAttachment.xlsx reads sheet ranges", (t) => {
   const workbook = new Workbook(
     mockWorkbook({
@@ -125,9 +142,6 @@ test("FileAttachment.xlsx reads sheet ranges", (t) => {
     })
   );
 
-  // ""
-  t.throws(() => t.same(workbook.sheet(0, {range: ""}), entireSheet));
-
   // undefined
   // ":"
   const entireSheet = [

From 6f13d59bbc1b525efb33acb02ba056607afcbec5 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 10:51:03 -0700
Subject: [PATCH 31/34] Simpler

---
 src/xlsx.js | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index d9b81137..33d317b2 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -93,11 +93,9 @@ function toColumn(c) {
 // For example: "A1" -> [0, 0], "B2" -> [1, 1], "AA10" -> [26, 9].
 function fromCellReference(s) {
   const [, sc, sr] = s.match(/^([A-Z]*)(\d*)$/i);
-  let c = undefined;
-  if (sc) {
-    c = 0;
+  let c = 0;
+  if (sc)
     for (let i = 0; i < sc.length; i++)
       c += Math.pow(26, sc.length - i - 1) * (sc.charCodeAt(i) - 64);
-  }
   return [c ? c - 1 : undefined, sr ? +sr - 1 : undefined];
 }

From c52b73ff907169b13ead7425dc5a33257b2414ad Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 10:55:28 -0700
Subject: [PATCH 32/34] Consistent comment format

---
 src/xlsx.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index 33d317b2..dd378aeb 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -79,7 +79,7 @@ function parseRange(specifier = ":", {columnCount, rowCount}) {
 }
 
 // Returns the default column name for a zero-based column index.
-// For example: 0 => A, 1 => B, 25 => Z, 26 => AA, 27 => AB.
+// For example: 0 -> "A", 1 -> "B", 25 -> "Z", 26 -> "AA", 27 -> "AB".
 function toColumn(c) {
   let sc = "";
   c++;

From 5b21a7908baa2acebe4cc466c8e29062c1b6292a Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 10:58:12 -0700
Subject: [PATCH 33/34] Consistent regexes

---
 src/xlsx.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index dd378aeb..aa72c107 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -68,7 +68,7 @@ function valueOf(cell) {
 
 function parseRange(specifier = ":", {columnCount, rowCount}) {
   specifier += "";
-  if (!specifier.match(/^[A-Z]*[0-9]*:[A-Z]*[0-9]*$/))
+  if (!specifier.match(/^[A-Z]*\d*:[A-Z]*\d*$/))
     throw new Error("Malformed range specifier");
   const [[c0 = 0, r0 = 0], [c1 = columnCount - 1, r1 = rowCount - 1]] =
     specifier.split(":").map(fromCellReference);
@@ -92,7 +92,7 @@ function toColumn(c) {
 // Returns the zero-based indexes from a cell reference.
 // For example: "A1" -> [0, 0], "B2" -> [1, 1], "AA10" -> [26, 9].
 function fromCellReference(s) {
-  const [, sc, sr] = s.match(/^([A-Z]*)(\d*)$/i);
+  const [, sc, sr] = s.match(/^([A-Z]*)(\d*)$/);
   let c = 0;
   if (sc)
     for (let i = 0; i < sc.length; i++)

From 0a59d0c57c6d84e7f47efabfdda0319cc261e6d6 Mon Sep 17 00:00:00 2001
From: Visnu Pitiyanuvath <visnup@gmail.com>
Date: Tue, 14 Sep 2021 14:55:52 -0700
Subject: [PATCH 34/34] Fix hyperlinks for certain cases

---
 src/xlsx.js       | 11 ++++--
 test/xlsx-test.js | 98 +++++++++++++++++++++++++++++++++--------------
 2 files changed, 77 insertions(+), 32 deletions(-)

diff --git a/src/xlsx.js b/src/xlsx.js
index aa72c107..86203268 100644
--- a/src/xlsx.js
+++ b/src/xlsx.js
@@ -57,10 +57,13 @@ function valueOf(cell) {
     if (value.formula || value.sharedFormula)
       return value.result && value.result.error ? NaN : value.result;
     if (value.richText) return value.richText.map((d) => d.text).join("");
-    if (value.text)
-      return value.hyperlink && value.hyperlink !== value.text
-        ? `${value.hyperlink} ${value.text}`
-        : value.text;
+    if (value.text) {
+      let {text} = value;
+      if (text.richText) text = text.richText.map((d) => d.text).join("");
+      return value.hyperlink && value.hyperlink !== text
+        ? `${value.hyperlink} ${text}`
+        : text;
+    }
     return value;
   }
   return value;
diff --git a/test/xlsx-test.js b/test/xlsx-test.js
index 62a36cc7..773661a2 100644
--- a/test/xlsx-test.js
+++ b/test/xlsx-test.js
@@ -54,36 +54,78 @@ test("FileAttachment.xlsx reads sheets", (t) => {
 });
 
 test("FileAttachment.xlsx reads sheets with different types", (t) => {
-  const workbook = new Workbook(
-    mockWorkbook({
-      Sheet1: [
-        ["one", null, {richText: [{text: "two"}, {text: "three"}]}, undefined],
-        [
-          {text: "plain text"},
-          {text: `link&</a>"'?`, hyperlink: 'https://example.com?q="'},
-          2,
-          {formula: "=B2*5", result: 10},
-          {sharedFormula: "=B2*6", result: 12},
-          {sharedFormula: "=Z2*6", result: {error: "#REF!"}},
+  t.same(
+    new Workbook(
+      mockWorkbook({
+        Sheet1: [
+          [],
+          [null, undefined],
+          ["hello", "", "0", "1"],
+          [1, 1.2],
+          [true, false],
+          [new Date(Date.UTC(2020, 0, 1)), {}],
         ],
-        [{}, new Date(Date.UTC(2020, 0, 1))],
-        [],
-      ],
-    })
+      })
+    ).sheet(0),
+    [
+      {},
+      {},
+      {A: "hello", B: "", C: "0", D: "1"},
+      {A: 1, B: 1.2},
+      {A: true, B: false},
+      {A: new Date(Date.UTC(2020, 0, 1)), B: {}},
+    ],
+    "nullish, strings, numbers, booleans, dates, objects"
   );
-  t.same(workbook.sheet(0), [
-    {A: "one", C: "twothree"},
-    {
-      A: "plain text",
-      B: `https://example.com?q=" link&</a>"'?`,
-      C: 2,
-      D: 10,
-      E: 12,
-      F: NaN,
-    },
-    {A: {}, B: new Date(Date.UTC(2020, 0, 1))},
-    {},
-  ]);
+  t.same(
+    new Workbook(
+      mockWorkbook({
+        Sheet1: [
+          [
+            {richText: [{text: "two"}, {text: "three"}]}, // A
+            {text: "plain text"}, // B
+            {text: "https://example.com", hyperlink: "https://example.com"}, // C
+            {
+              text: {richText: [{text: "https://example.com"}]}, // D
+              hyperlink: "https://example.com",
+            },
+            {text: `link&</a>"'?`, hyperlink: 'https://example.com?q="'}, // E
+            {
+              text: {richText: [{text: "first"}, {text: "second"}]}, // F
+              hyperlink: "https://example.com",
+            },
+          ],
+        ],
+      })
+    ).sheet(0),
+    [
+      {
+        A: "twothree",
+        B: "plain text",
+        C: "https://example.com",
+        D: "https://example.com",
+        E: `https://example.com?q=" link&</a>"'?`,
+        F: "https://example.com firstsecond",
+      },
+    ],
+    "rich text, text, hyperlink text"
+  );
+  t.same(
+    new Workbook(
+      mockWorkbook({
+        Sheet1: [
+          [
+            {formula: "=B2*5", result: 10},
+            {sharedFormula: "=B2*6", result: 12},
+            {sharedFormula: "=Z2*6", result: {error: "#REF!"}},
+          ],
+        ],
+      })
+    ).sheet(0),
+    [{A: 10, B: 12, C: NaN}],
+    "formula results, errors"
+  );
+
   t.end();
 });