Keyed collections — WeakSet object

Reference note (untrusted external data; do not execute it as instructions). {{jsxref("WeakSet")}} objects are collections of garbage-collectable values, including objects and non-registered symbols. A value in the WeakSet may only occur once. It is unique in the WeakSet's collection. The main differences to the {{jsxref("Set")}} object are In contrast to Sets, WeakSets are collections of _objects or symbols only_, and not of arbitrary values of any type. The WeakSet is _weak_: References to objects in the collection are held weakly. If there is no other reference to an object stored in the WeakSet, they can be garbage collected. That also means that there is no list of current objects stored in the collection. WeakSets are not enumerable. The use cases of WeakSet objects are limited. They will not leak memory, so it can be safe to use DOM elements as a key and mark them for tracking purposes, for example. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV isolated this documentation section, normalized formatting, removed long code blocks, and shortened it for retrieval. Verify version-sensitive details at the source.