[BUG] ExcelJS 4.1.0 is not working with Angular 9 in IE11

🐛 Bug Report

Lib version: 4.1.0 angular: 9.0.7

I have used polyfill code for unicode but still its giving error “Invalid range in character set” in polyfill.ts in IE11

unicode-regex-polyfill.js

import 'core-js/modules/es.promise';
import 'core-js/modules/es.object.assign';
import 'core-js/modules/es.object.keys';
import 'regenerator-runtime/runtime';
import rewritePattern from 'regexpu-core';
import { generateRegexpuOptions } from '@babel/helper-create-regexp-features-plugin/lib/util';

// const { RegExp } = global;
try {
  new RegExp('a', 'u');
} catch (err) {
  // @ts-ignore
  global.RegExp = function(pattern, flags) {
    if (flags && flags.includes('u')) {
      return new RegExp(
        rewritePattern(
          pattern,
          flags,
          generateRegexpuOptions({ flags, pattern })
        )
      );
    }
    return new RegExp(pattern, flags);
  };
  // @ts-ignore
  global.RegExp.prototype = RegExp;
}

polyfill.js

....
....
....
import 'zone.js/dist/zone'; // Included with Angular CLI.
import 'unicode-regex-polyfill.js';
import 'exceljs';
....
....

[simonigreen]

I made a poor man’s polyfill that doesn’t require importing any extra modules like babel. It just discards unicode flag in RegExps and erases parts of the patterns used in exceljs that require unicode support. It’s pretty dirty but it allowed our app to work in IE and even exceljs seems to still do its job.

// Add this code to polyfills.ts

const { RegExp } = window;
try {
    new RegExp('a', 'u');
} catch (err) {
    // @ts-ignore
    window.RegExp =
        (pattern: string, flags: string | undefined) => {
            if (flags?.includes('u') === true) {
                // Ignore unicode flag in RegExp
                flags = flags === 'u' ? undefined : flags.replace('u', '');
                // Discard parts of the patterns used by exceljs that error out in non-unicode RegExps.
                pattern = pattern.replace(/\uDC00-\uDBFF/g, '');
                pattern = pattern.replace(/\uDC00-\uDB7F/g, '');

                return new RegExp(pattern, flags);
            }
            return new RegExp(pattern, flags);
        };
    // @ts-ignore
    window.RegExp.prototype = RegExp;
}

I found that this polyfill worked however the last line needed to be changed to avoid breaking other libraries that might access the prototype of RegExp. Changing the line window.RegExp.prototype = RegExp; to the following fixed the issue and allowed me to use version 4.2.1 of ExcelJS:

window.RegExp.prototype = RegExp.prototype;

[ThomasKruegl]

I got this working using:

polyfill.ts

import 'core-js/es6/promise';
import 'core-js/es7/symbol';
import 'core-js/es7/object';
import 'regenerator-runtime/runtime';
import './unicode-regex-polyfill';
import 'exceljs/dist/exceljs';

unicode-regex-polyfill.ts:

import rewritePattern from 'regexpu-core';
import { generateRegexpuOptions } from '@babel/helper-create-regexp-features-plugin/lib/util';

const { RegExp } = window;
try {
  new RegExp('a', 'u');
} catch (err) {
  // @ts-ignore
  window.RegExp = function(pattern, flags) {
    if (flags && flags.includes('u')) {
      return new RegExp(
        rewritePattern(
          pattern,
          flags,
          generateRegexpuOptions({ flags, pattern })
        )
      );
    }
    return new RegExp(pattern, flags);
  };
  // @ts-ignore
  window.RegExp.prototype = RegExp;
}

Replaced global with window, and adjusted some polyfill imports.

I added “import ‘exceljs/dist/exceljs’;” before the zone polyfill for angular, because zone complained about Promise being changed, and i remembered this as workaround from another issue.

Also i used “import ‘exceljs/dist/exceljs’;” instead of “import ‘exceljs’;” everywhere, not only in the polyfill.ts. I did NOT use “import ‘exceljs/dist/es5’;” because that somehow got a lot of code in node_modules into the typescript compiler scope, and produced errors for missing fs module (which is fine on windows) and other stuff.

BUT:

• this is experimental
• when accessing the functionality, IE hung, said something about long running script, and only after >30 seconds, i got my excel. Same thing in Chrome takes 1 or 2 seconds.
• reading an excel still failed, “Object doesn’t support property or method ‘arrayBuffer’” - still examining that one.