ECMAScript6 WeakMap polyfill.

$ npm install --save weakmap-polyfill

Import or require weakmap-polyfill, then WeakMap will be defined in the global scope if native WeakMap is not supported in running environment.

import 'weakmap-polyfill'; const weakMap = new WeakMap();

require('weakmap-polyfill'); var weakMap = new WeakMap();

<script src="weakmap-polyfill.min.js"></script> <script> var weakMap = new WeakMap(); </script>

• Chrome 15
• Firefox 3
• IE 7
• Safari 4
• Opera 11.5
• Edge

• Browser Test
• Browser Test for Legacy

This polyfill has following few limitations.

• WeakMap iterable argument is not supported. (23.3.1.1 WeakMap ( [ iterable ] ))
• Frozen and sealed objects are not supported.
• The values held by a WeakMap can't be collected once the map itself is GCed, since the values here are tied to the keys. #4

MIT