Izmjenjena struktura, dodan backand

web/node_modules/core-js/modules/es6.weak-set.js

@@ -0,0 +1,12 @@
+'use strict';
+var weak = require('./$.collection-weak');
+
+// 23.4 WeakSet Objects
+require('./$.collection')('WeakSet', function(get){
+  return function WeakSet(){ return get(this, arguments.length > 0 ? arguments[0] : undefined); };
+}, {
+  // 23.4.3.1 WeakSet.prototype.add(value)
+  add: function add(value){
+    return weak.def(this, value, true);
+  }
+}, weak, false, true);