JS 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 (e.g. IE < 11) or which have non-compliant implementations (e.g. IE 11), 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') );