Web platform features explorer

The when() method on a event target returns an Observable object, which provides a declarative API for subscribing to and operating on events. It's an alternative to addEventListener() callbacks.

Status

Limited availability

This feature received a negative standards position from at least one browser vendor. It's very unlikely to ever become Baseline in this current form.

MDN documentation

No MDN documentation found. You can search for the feature on MDN. If you believe that MDN has no documentation about this feature, you can open an issue on MDN's GitHub repository.

Specifications

Observable, from Web Platform Incubator Community Group (W3C).

Browser support

Chrome 135 Released on 2025-04-01
Chrome Android 135 Released on 2025-04-01
Edge 135 Released on 2025-04-04
Firefox ❌ See bugzil.la/1871732 Vendor position : negative (concerns: complexity, venue, API design)
Firefox for Android ❌ Vendor position : negative (concerns: complexity, venue, API design)
Safari ❌ Vendor position : support (concerns: venue)
Safari on iOS ❌ Vendor position : support (concerns: venue)

Usage (according to Chrome Platform Status)

~0.000% of page loads. More data at chromestatus.com.

Web Platform Tests (WPT)

View the latest WPT test results for this feature

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