Fix #3028: make getWorksheet case-insensitive to match addWorksheet

FORK.md

@@ -28,6 +28,16 @@ This AI-assisted workflow enables rapid response to community issues while maint
 
 ## Fork Release History
 
+### Unreleased
+
+**Bug Fix: `workbook.getWorksheet(name)` is now case-insensitive** ([upstream #3028](https://github.com/exceljs/exceljs/issues/3028))
+
+`Workbook.addWorksheet(name)` already enforces case-insensitive uniqueness (and Excel itself treats sheet names case-insensitively), but `Workbook.getWorksheet(name)` was matching with a case-sensitive `===`. The two APIs disagreed: a workbook would refuse to add `"sheet1"` because `"Sheet1"` exists, yet `getWorksheet("sheet1")` would return `undefined` for that same sheet.
+
+`getWorksheet` now lowercases both sides of the comparison so any casing of an existing sheet name resolves to that sheet. Numeric-id and no-arg branches are unchanged.
+
+Minor behavior change: code that relied on a casing mismatch returning `undefined` will now find the sheet. We consider this a bug fix — the previous behavior contradicted `addWorksheet`'s own constraint.
+
 ### 4.4.0-protobi.9 (2026-02-01)
 
 **New Feature: Pivot Table & Chart Round-Trip Preservation** ([#41](https://github.com/cjnoname/excelts/issues/41))

lib/doc/workbook.js

@@ -57,20 +57,20 @@ class Workbook {
     // if options is a color, call it tabColor (and signal deprecated message)
     if (options) {
       if (typeof options === 'string') {
+        const argbMsg =
+          'tabColor argument is now deprecated. Please use workbook.addWorksheet(name, {properties: { tabColor: { argb: "rbg value" } }';
         // eslint-disable-next-line no-console
-        console.trace(
-          'tabColor argument is now deprecated. Please use workbook.addWorksheet(name, {properties: { tabColor: { argb: "rbg value" } }'
-        );
+        console.trace(argbMsg);
         options = {
           properties: {
             tabColor: {argb: options},
           },
         };
       } else if (options.argb || options.theme || options.indexed) {
+        const tabMsg =
+          'tabColor argument is now deprecated. Please use workbook.addWorksheet(name, {properties: { tabColor: { ... } }';
         // eslint-disable-next-line no-console
-        console.trace(
-          'tabColor argument is now deprecated. Please use workbook.addWorksheet(name, {properties: { tabColor: { ... } }'
-        );
+        console.trace(tabMsg);
         options = {
           properties: {
             tabColor: options,
@@ -79,13 +79,12 @@ class Workbook {
       }
     }
 
-    const lastOrderNo = this._worksheets.reduce((acc, ws) => ((ws && ws.orderNo) > acc ? ws.orderNo : acc), 0);
-    const worksheetOptions = Object.assign({}, options, {
-      id,
-      name,
-      orderNo: lastOrderNo + 1,
-      workbook: this,
-    });
+    let lastOrderNo = 0;
+    for (const w of this._worksheets) {
+      if (w && w.orderNo > lastOrderNo) lastOrderNo = w.orderNo;
+    }
+    const orderNo = lastOrderNo + 1;
+    const worksheetOptions = Object.assign({}, options, {id, name, orderNo, workbook: this});
 
     const worksheet = new Worksheet(worksheetOptions);
 
@@ -112,7 +111,9 @@ class Workbook {
       return this._worksheets[id];
     }
     if (typeof id === 'string') {
-      return this._worksheets.find(worksheet => worksheet && worksheet.name === id);
+      // Case-insensitive to match addWorksheet's uniqueness rule (and Excel itself).
+      const target = id.toLowerCase();
+      return this._worksheets.find(ws => ws && ws.name.toLowerCase() === target);
     }
     return undefined;
   }

spec/integration/issues/issue-3028-getworksheet-case-insensitive.spec.js

@@ -0,0 +1,46 @@
+const ExcelJS = verquire('exceljs');
+
+describe('github issues', () => {
+  describe('issue 3028 - workbook.getWorksheet should be case-insensitive', () => {
+    it('returns the same worksheet regardless of name casing', () => {
+      const wb = new ExcelJS.Workbook();
+      const ws = wb.addWorksheet('TestSheet');
+
+      expect(wb.getWorksheet('TestSheet')).to.equal(ws);
+      expect(wb.getWorksheet('testsheet')).to.equal(ws);
+      expect(wb.getWorksheet('TESTSHEET')).to.equal(ws);
+      expect(wb.getWorksheet('tEsTsHeEt')).to.equal(ws);
+    });
+
+    it('still returns undefined for genuinely unknown names', () => {
+      const wb = new ExcelJS.Workbook();
+      wb.addWorksheet('TestSheet');
+
+      expect(wb.getWorksheet('OtherSheet')).to.equal(undefined);
+    });
+
+    it('preserves numeric id lookup', () => {
+      const wb = new ExcelJS.Workbook();
+      const ws = wb.addWorksheet('TestSheet');
+
+      expect(wb.getWorksheet(ws.id)).to.equal(ws);
+    });
+
+    it('preserves the no-arg first-worksheet shortcut', () => {
+      const wb = new ExcelJS.Workbook();
+      const ws = wb.addWorksheet('TestSheet');
+
+      expect(wb.getWorksheet()).to.equal(ws);
+    });
+
+    it('aligns getWorksheet with addWorksheet case-insensitive uniqueness', () => {
+      // addWorksheet rejects "testsheet" as a duplicate of "TestSheet";
+      // therefore getWorksheet("testsheet") must locate the existing sheet.
+      const wb = new ExcelJS.Workbook();
+      const ws = wb.addWorksheet('TestSheet');
+
+      expect(() => wb.addWorksheet('testsheet')).to.throw(/already exists/);
+      expect(wb.getWorksheet('testsheet')).to.equal(ws);
+    });
+  });
+});