Microsoft has begun development to include support for asm.js in its Chakra JavaScript engine, as part of a plan to boost JavaScript execution speed with Chakra in Windows 10. Asm.js uses a subset of JavaScript that can compile code to run at near native speeds in the browser, bringing with it significant speed improvements.
It works by taking code, typically written in C or C++, and “transpiling” it to run on a web engine, using the likes of WebGL and WebAudio. That transpiled code can then be run at significantly faster speeds by using a narrow set of well-defined interger and floating point operations, according to Wikipedia. Because asm.js runs on a strict subset of JavaScript, it can work interoperably across platforms and browsers, meaning that if a website coded with asm.js is run on a browser that supports it, it will “light up” the code with speed improvements, but will run fine on browsers that don’t support the improvements.
Asm.js began as a feature of Firefox 22, in July of 2013, and has been in Chrome since Chrome 28 in the same time frame. Its inclusion in IE/Chakra has been one of the most requested features in the IE Suggestion Box on UserVoice, and judging by the comments in the IE Blog post announcing the news, developers are excited to have it coming in Windows 10 / Spartan.
