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An essentialWeakMap polyfill for legacy browsers (IE < 11).

• CDN viahttps://unpkg.com/@ungap/weakmap
• ESM viaimport WeakMap from '@ungap/weakmap'
• CJS viaconst WeakMap = require('@ungap/weakmap')

Compatible down to IE9, works well with ES5 shim upfront in IE8 (and maybe lower too).

Live test

If you need this module to work in IE < 11 too with frozen objects, or template literals frozen via Babel transpilation, you need to either nullifyObject.freeze and others via something like<script>this.WeakMap||(Object.freeze=Object);</script> on top of your pages, or you can nullify only template literals through:

<script>this.WeakMap||(function(O,f){f=O.freeze||O;O.freeze=function(o){return'raw'ino?o:f(o)}}(Object));</script>