The newest Chrome Beta channel release includes new JavaScript language features, an improved audio experience on Android, and a large number of minor API improvements and deprecations. Unless otherwise noted, changes described below apply to Chrome for Android, Windows, Mac, Linux, and Chrome OS.

New ES2015 features

Over the past year Chrome has shipped a number of new JavaScript features defined in the ES2015 specification (formerly known as ES6), a major update to JavaScript that allows developers to write application logic that is easier to read, more powerful, and more memory efficient than ever before.

Service worker improvements

Chrome 40 introduced support for service workers, enabling developers to build high performance sites that work offline. This release includes a number of improvements:

Finally, in a breaking change, messages sent via Client.postMessage() now fire an event on navigator.serviceWorker instead of the window object.

Media controls in Android notifications

Playback controls for currently-playing audio are shown in the notification tray and on the lock screen

On Android, native apps can show media controls in a system notification when playing audio, making it easy for users to control audio while multitasking. Chrome 45 brings this capability to the web by showing a notification with media controls when audio is playing in web content. The controls will automatically show up when <audio> or <video> tags play audio longer than 5 seconds.

Other updates in this release

Update: The User Timing and Resource Timing APIs are unfortunately not exposed to service workers in this release, but should be available in Chrome 46. As always, visit for a complete overview of Chrome’s developer features, and circle +Google Chrome Developers for more frequent updates.

Posted by Andreas Rossberg, Software Engineer and ECMAScript Evangelizer