An essential WeakSet poorlyfill legacy browsers that don't have even a WeakMap but need just a WeakSet.
- CDN via https://unpkg.com/@ungap/essential-weakset
- ESM via
import WeakSet from '@ungap/essential-weakset' - CJS via
const WeakSet = require('@ungap/essential-weakset')
Compatible down to IE9, works well with ES5 shim upfront in IE8 (and maybe lower too).