Ensure IE11 compatiblity for unicode regex patterns

README.md

@@ -197,11 +197,29 @@ require('core-js/modules/es.object.assign');
 require('core-js/modules/es.object.keys');
 require('regenerator-runtime/runtime');
 
-// ...
-
 const ExcelJS = require('exceljs/dist/es5');
 ```
 
+For IE 11, you'll also need a polyfill to support unicode regex patterns. For example,
+
+```js
+const rewritePattern = require('regexpu-core');
+const {generateRegexpuOptions} = require('@babel/helper-create-regexp-features-plugin/lib/util');
+
+const {RegExp} = global;
+try {
+  new RegExp('a', 'u');
+} catch (err) {
+  global.RegExp = function(pattern, flags) {
+    if (flags && flags.includes('u')) {
+      return new RegExp(rewritePattern(pattern, flags, generateRegexpuOptions({flags, pattern})));
+    }
+    return new RegExp(pattern, flags);
+  };
+  global.RegExp.prototype = RegExp;
+}
+```
+
 ## Browserify
 
 ExcelJS publishes two browserified bundles inside the dist/ folder:

lib/exceljs.browser.js

@@ -1,9 +1,26 @@
 /* eslint-disable import/no-extraneous-dependencies,node/no-unpublished-require */
 require('core-js/modules/es.promise');
+require('core-js/modules/es.string.includes');
 require('core-js/modules/es.object.assign');
 require('core-js/modules/es.object.keys');
 require('regenerator-runtime/runtime');
 
+const rewritePattern = require('regexpu-core');
+const {generateRegexpuOptions} = require('@babel/helper-create-regexp-features-plugin/lib/util');
+
+const {RegExp} = global;
+try {
+  RegExp('a', 'u');
+} catch (err) {
+  global.RegExp = function(pattern, flags) {
+    if (flags && flags.includes('u')) {
+      return new RegExp(rewritePattern(pattern, flags, generateRegexpuOptions({flags, pattern})));
+    }
+    return new RegExp(pattern, flags);
+  };
+  global.RegExp.prototype = RegExp;
+}
+
 const ExcelJS = {
   Workbook: require('./doc/workbook'),
 };

package.json

@@ -105,6 +105,7 @@
   "devDependencies": {
     "@babel/cli": "^7.6.4",
     "@babel/core": "^7.9.0",
+    "@babel/helper-create-regexp-features-plugin": "^7.8.8",
     "@babel/preset-env": "^7.9.0",
     "@types/chai": "^4.2.11",
     "@types/mocha": "^5.2.7",
@@ -138,6 +139,7 @@
     "prettier-eslint": "^9.0.0",
     "prettier-eslint-cli": "^5.0.0",
     "regenerator-runtime": "^0.13.5",
+    "regexpu-core": "^4.7.0",
     "semver": "^5.6.0",
     "ts-node": "^8.8.1",
     "typescript": "^3.8.3"