Ergonomic brand checks for private fields

Category: JavaScript
Type: Chromium catches up
Status: Enabled by default (Chrome 91)
Intent stage: Start prototyping

Breaking change: No
Enterprise impact: None
Chromium flag: --harmony-staging
Spec maturity: Incubation
Web Platform Tests: No

WPT details: Will be tested by test262, won't be tested by WPT.

Summary

This JavaScript feature adds the capability for testing the existence of a private field in an object: "#foo in obj" Proposal: https://github.com/tc39/proposal-private-fields-in-in The feature has reached Stage 3 in TC39.

Motivation

See proposal https://github.com/tc39/proposal-private-fields-in-in for motivating examples.

Standards & signals

Specification: https://github.com/tc39/proposal-private-fields-in-in
Firefox: No signal — This is a minor, uncontroversial TC39 stage 3 feature.
Safari: No signal — This is a minor, uncontroversial TC39 stage 3 feature.
Web developers: No signals — N/A. This is a minor, uncontroversial TC39 stage 3 feature.
Tracking bug: https://bugs.chromium.org/p/v8/issues/detail?id=11374

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=ergonomic-brand-checks-for-private-fields
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+Ergonomic%20brand%20checks%20for%20private%20fields
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=Ergonomic%20brand%20checks%20for%20private%20fields
Baseline status: https://webstatus.dev/?q=Ergonomic%20brand%20checks%20for%20private%20fields

View on chromestatus.com