@ungap/essential-weakset/min.js

Essential WeakSet for legacy browsers.

/*! (c) Andrea Giammarchi - ISC */
var self=this||{};try{self.WeakSet=WeakSet}catch(t){!function(t,e){var a=n.prototype;function n(){"use strict";e(this,"_",{value:"_@ungap/weakmap"+t++})}a.add=function(t){return this.has(t)||e(t,this._,{value:!0,configurable:!0}),this},a.has=function(t){return this.hasOwnProperty.call(t,this._)},a.delete=function(t){return this.has(t)&&delete t[this._]},self.WeakSet=n}(Math.random(),Object.defineProperty)}