Support developing in IE 9

I have created a new reactjs project using create-react-app and am finding it’s not working on IE10 & IE9. I have done a lot of research and it led me to using polyfills, which I have done with many of my other Rails on React app, but I’m finding it not working with this project created via create-react-app.

Here’s the error:

SCRIPT5009: 'Map' is undefined

I notice this error is related to ES6’s new Map() function.

So, here’s what I’ve done in my code in an attempt to make it work:

import './polyfill';
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import { BrowserRouter } from 'react-router-dom';
import 'bootstrap/dist/css/bootstrap.min.css';

const app = (
  <BrowserRouter basename={process.env.PUBLIC_URL}>
    <App />
  </BrowserRouter>
);

ReactDOM.render(app, document.getElementById('root'));

Polyfill.js:

import 'core-js/es6/map';
import 'core-js/es6/set';
import 'core-js/fn/object/assign';

This isn’t working. I’m not sure what else to try. I’ve tried a lot of other polyfill imports as well and continue to get the same error.

Any help would be appreciated!

[lujb]

@ivoborisov I have also got sucked into this problem recently, and I can’t wait the release of 3.0 to develop in IE 9, so I spent hours to fix it locally.

This problem is caused by react-dev-utils/webpackHotDevClient provided by CRA to bring better user experience. The custom webpackHotDevClient introduced chalk module accidentally which in turn have a dependency of ansi-style module, and the final module used es6 Map feature which sucks in IE 9. Unfortunately, webpackHotDevClient is loaded prior to the polyfilled app code, so IE 9 complaines that ‘Map’ is undefined.

Fix: Eject CRA locally and then locate the entry config in config/webpack.config.dev.js .

1. exchange the position of the two entries OR
2. use the stock client OR
3. remove the chalk code in react-dev-utils/webpackHotDevClient (chalk seems unnessesary)

[Timer]

It is a known limitation that the dev server does not support IE9/11. We’re working on adding this.