This is an experimental technology, part of the Harmony (ECMAScript 6) proposal. Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future version of browsers as the spec changes.
The WeakSet.prototype property represents the prototype for the WeakSet constructor.
Property attributes of WeakSet.prototype
WeakSet instances inherit from WeakSet.prototype. You can use the constructor's prototype object to add properties or methods to all WeakSet instances.
Returns the function that created an instance's prototype. This is the WeakSet function by default.