is-implemented.js•621 B
"use strict";
module.exports = function () {
var weakMap, obj;
if (typeof WeakMap !== "function") return false;
try {
// WebKit doesn't support arguments and crashes
weakMap = new WeakMap([[obj = {}, "one"], [{}, "two"], [{}, "three"]]);
} catch (e) {
return false;
}
if (String(weakMap) !== "[object WeakMap]") return false;
if (typeof weakMap.set !== "function") return false;
if (weakMap.set({}, 1) !== weakMap) return false;
if (typeof weakMap.delete !== "function") return false;
if (typeof weakMap.has !== "function") return false;
if (weakMap.get(obj) !== "one") return false;
return true;
};