In the June 2015 Microsoft introced preview supports for asm.js and it is now supported by default in Microsoft Edge starting with Microsoft EdgeHTML 13.10532. asm-optimized code will be helpful and Hosted Web Applications and the WebView in any Universal Windows Application can now benefitted.
What is asm.js?
From Microsoft Site:
To demonstrate the asm.js performance MS has given a demo with chess battle
Launch F12, navigate to the Debugger tab and disconnect the debugger using the connect/disconnect debugger button:
Next, switch to the Console tab and view all console messages there.
You can try it out yourself in the Windows 10 Insider Preview fast or slow rings. On the stable release of Microsoft Edge, you can enable asm.js for Microsoft Edge by navigating to about:flags.
In addition to Chess Battle demo, several other asm.js demos are available online for you to explore and to have some fun with, including Angry Bots, Tappy Chicken, ogv.js, and the demos listed here