1. This is about JS speed. How important is JS speed in mobile apps, compared to rendering for example? That's the crucial question here, and I don't see any numbers on it. Rendering, after all, should be the same speed as a native app.
2. "Nothing terribly important has happened to CPU-bound JavaScript lately" - picking some benchmarks where there has been little change is possible. There are also benchmarks where there have been large changes. For example, many browsers now have incremental GC and background thread JITing. In some workloads these make a huge difference - but perhaps not on the old SunSpider benchmark.
edit: As an example of a type of code that can run far faster today than before, see Box2D, which is a realistic codebase since many mobile games use it: http://j15r.com/blog/2013/07/05/Box2d_Addendum
Canvas is only marginally slower than the native 2D drawing APIs (it is a thin wrapper for Skia on Android and CoreGraphics on iOS), but it still uses only a single CPU thread for drawing on both platforms. To use the GPU, one has to turn to the -webkit-transform CSS property which, under certain circumstances, promotes the element to a GPU buffer. Only once WebGL becomes accessible will the mobile web have a drawing API that is more efficient than the standard windowing APIs.
1. This is about JS speed. How important is JS speed in mobile apps, compared to rendering for example? That's the crucial question here, and I don't see any numbers on it. Rendering, after all, should be the same speed as a native app.
2. "Nothing terribly important has happened to CPU-bound JavaScript lately" - picking some benchmarks where there has been little change is possible. There are also benchmarks where there have been large changes. For example, many browsers now have incremental GC and background thread JITing. In some workloads these make a huge difference - but perhaps not on the old SunSpider benchmark.
edit: As an example of a type of code that can run far faster today than before, see Box2D, which is a realistic codebase since many mobile games use it: http://j15r.com/blog/2013/07/05/Box2d_Addendum