16 var m1 = new WeakSet();  variable
19 assert (m1.add (k1) instanceof WeakSet);
20 assert (m1.has (k1) === true);
25 assert (m1.has (k1) === false);
26 assert (m1.delete(k1) === false);
27 assert (m1.add (k1) instanceof WeakSet);
28 assert (m1.has (k1) === true);
30 assert (m1.delete ("str") === false);
31 assert (m1.has (42) === false);
34   m1.add (42);
41 assert (m1.delete(k1) === true);
43 assert (m1.has (k1) === false);
48 assert (m1.add (k1) instanceof WeakSet);
49 assert (m1.has (k1) === true);
59 m1.add (k1);
60 m1.add (k2);
91 m1 = new WeakSet([k1, k2]);  variable
92 assert (m1.has (k1));
93 assert (m1.has (k2));
95 m1 = undefined;
98 m1 = new WeakSet();  variable
100 m1.add (k1);
101 m1.add (k1);
102 m1.add (k1);
103 assert (m1.has (k1));
107 m1 = new WeakSet();  variable
108 m1.add (k1);
109 m1.add (k1);
110 m1.add (k1);
111 assert (m1.has (k1));
112 m1 = new WeakSet();  variable
146 m1.add([]);