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WebAssembly and the Future of JavaScript
Nerval's Lobster writes: WebAssembly is the next stage in the evolution of client-side scripting. In theory, it will improve on JavaScript's speed. That's not to say that JavaScript is a slowpoke: Incremental speed improvements have included the rollout of asm.js (an optimized subset) in 2013. But WebAssembly—while not a replacement for JavaScript—is intended as a "cure" for a variety of issues where JavaScript isn't always a perfect fit, including video editing, encryption, peer-to-peer, and more. (Here's a full list of the Web applications that WebAssembly could maybe improve.) If WebAssembly is not there to replace JavaScript but to complement it, the key to the integration rests with the DOM and Garbage Collected Objects such as JavaScript strings, functions (as callable closures), Typed Arrays and Typed objects. The bigger question is, will WebAssembly actually become something big, or is it ultimately doomed to suffer the fate of other hyped JavaScript-related platforms such as Dart (a Google-only venture), which attracted buzz ahead of a Minimum Viable Product release, only to quickly fade away afterward?
You can write asm.js by hand, no so sure about WebAssembly, although there could be rare corner cases where this is warranted.
But in almost all cases this is not the expected deployment scenario. Rather, you'll write your web app in one of many different high-level languages, and it will get compiled to WebAssembly. Interestingly enough, one of these languages is C++, which has a vastly different thread and memory model compared to JavaScript. This has always been a big stumbling block as there is existing C++ code that people would like to run in browsers, but up to now there was no good solution that works across browsers.
The roadmap suggests that JavaScript will retain its robust memory and thread model, but gain enough features to support the less robust but higher-performant model used by C++. We truly live in interesting times.
This will also address the problem that JavaScript could never effectively take advantage of multiple cores, but CPUs tend to add more performance by adding cores rather than by improving single-thread throughput.