Summary: This feature allows developers to create weak references to JavaScript objects. Finalizers are also provided that allow developers to perform actions when an object is garbage collected, without keeping that object alive.
This is an advanced feature that is not expected to be widely used but is necessary for some use important use cases such as exposing WebAssembly memory to JavaScript. Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1561074 Standard: Proposal: https://github.com/tc39/proposal-weakrefs JS spec changes: https://tc39.es/proposal-weakrefs/ HTML spec changes: https://github.com/whatwg/html/pull/4571 The proposal is at stage 3. Platform coverage: This is a new JavaScript language feature and will be available in all contexts. Preference: This feature will be controlled by the javascript.options.weakrefs pref, which will be off by default. DevTools bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1589707 Other browsers: Chrome: implemented behind a flag Safari: believed to have an implementation web-platform-tests: There are test262 tests covering this feature: https://github.com/tc39/test262/tree/master/test/built-ins/WeakRef https://github.com/tc39/test262/tree/master/test/built-ins/FinalizationGroup Web platform tests will be added in the following bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1589714 Secure contexts: This is a JS language feature and is thus present in all contexts where scripts are executed. Is this feature enabled by default in sandboxed iframes? If not, is there a proposed sandbox flag to enable it? If allowed, does it preserve the current invariants in terms of what sandboxed iframes can do? Where enabled, this feature will be allowed by default in sandboxed iframes. It does not change the invariants in terms of what sandboxed iframes can do. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
