WeakSet.prototype.has()

The has() method returns a boolean indicating whether an object exists in a WeakSet or not.

ws.has(value);

value

Required. The object to test for presence in the WeakSet.

Boolean

Returns true if an element with the specified value exists in the WeakSet object; otherwise false.

var ws = new WeakSet();
var obj = {};
ws.add(window);

mySet.has(window);  // returns true
mySet.has(obj);     // returns false

• WeakSet
• WeakSet.prototype.add()
• WeakSet.prototype.delete()