gaearon/React 16 JavaScript Environment.md

## React 16 JavaScript Environment.md

      
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              React 16 JavaScript Environment.md
            
          
    JavaScript Environment Requirements

React 16 depends on the collection types Map and Set. If you support older browsers and devices which may not yet provide these natively (eg <IE11), consider including a global polyfill in your bundled application, such as core-js or babel-polyfill.
A polyfilled environment for React 16 using core-js to support older browsers might look like:
import 'core-js/es6/map';
import 'core-js/es6/set';

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <h1>Hello, world!</h1>,
  document.getElementById('root')
);
React also depends on requestAnimationFrame (even in test environments). A simple shim for testing environments would be:
global.requestAnimationFrame = function(callback) {
  setTimeout(callback, 0);
};