What's the current status of Javascript ES5?

Question

What browsers / engines already support ES5 [strict]?

Answer 1

All the major browser vendors more or less have had ES5 fully implemented for a few years now (though IE 9 doesn't support strict mode). kangax created this compatibility table representing the existence of ECMAScript 5 features in major browsers and other JS implementations. It will even list the availability of those features in the browser you visit the page with. It doesn't test conformance, however.

Kris Kowal created es5-shim.js, which provides as much of the functionality of ES5 as possible to ES3 compliant implementations. Of course, not everything is possible but the goal of the shim is to allow code to gracefully degrade.

Answer 2

AFAIK, the only implementation of ECMAScript 5 is BESEN. It's a bit disappointing, really. BESEN was created from scratch, by a single developer, in just a couple of weeks. Google, Microsoft, Apple, Mozilla and Opera on the other hand, with all their developers, all their money, haven't been able to provide an implementation after almost 11 months. And that is despite the fact that they have dozens of developers, have an already working implementation as a base to start from, were a part of the standardization process from day one (and thus had access to the specs long before the author of BESEN did), and most of the features in the ES5 specification were taken from already existing implementations in the browsers.

AFAIK, the only two features that in ECMAScript 5 that were not already part of JavaScript were the Properties API and Strict Mode.

Answer 3

This page of the ecmascript wiki has links to the bugs remaining in the major implementations in progress.