Intel has been trying to increase performance of browser-based applications that need to access SIMD instructions on the host processor and use data parallelism.
Intel wants to get SIMD.js capabilities in ECMAscript 7, which may not arrive for some time. ECMAscript 6, for its part which should be ready later this year.
SIMD capabilities have already been implemented to an extent in Firefox nightly, and I think the full JIT support will be there in a couple of months. Intel has also submitted the full patch to Chromium V8 for review." SIMD.js has been included in Intel's Crosswalk Web runtime and distributed in the company's XDK tool for HTML5 mobile application development.