JavaScript: Same Code, and a Standardized Test Suite

June 25th, 2010

Being all in with HTML5 means being committed to enabling developers to use the Same Markup on the Web, and that includes the same JavaScript code.

The Chakra JavaScript engine in the latest Platform Preview release of Internet Explorer 9 includes significantly improved support for the ECMAScript (ECMA-262) standard, including features new to the recently finalized ECMAScript Fifth Edition (often called ES5 for short). This also includes complete support for JavaScript tests in Bucket 6 of the Acid3 test suite. Microsoft has been a key contributor to the ES5 effort. During the drafting of ES5, Microsoft was the first to provide a private reference implementation of the specification along with conformance tests to the ECMA Technical Committee 39 (TC-39).

Having the same markup work correctly across the web requires comprehensive tests that all browsers can rely on to deliver interoperable implementations. Microsoft has worked with the W3C to provide definitive test suite specifications for HTML, CSS, SVG, and other web standards. In recent months, we’ve contributed nearly 200 new tests to the W3C for these standards.

Unlike specifications governed by W3C, JavaScript does not have a definitive test suite owned and sponsored by ECMA. In the absence of such a suite, browser vendors and others have tried to fill the gap. We have published a suite of tests for new features in ECMAScript 5 through Codeplex, and will soon publish them on the Internet Explorer Testing Center. Other browser vendors have their own test suites. While all these tests are useful, they also have inconsistencies: different coverage of standards, different test harnesses, and implementation issues. Many in the industry have questioned whether we should have a more consistent way to test ECMAScript by working together.

That’s why Microsoft is now working with other browser vendors and other members of TC-39 to create an official test suite for ECMAScript sponsored by ECMA. We plan to help build this test suite, and contribute tests to it. We also welcome other browser vendors’ contributions to this effort.

Ensuring the same script works everywhere is vital to web developers. We look forward to hearing your feedback as we can continue to work on making this a reality.


Shanku Niyogi
General Manager, JavaScript Team