For example, even though IndexedDB uses LevelDB under the hood in Chrome, it's much slower (and many times slower than KV stores outside the browser on the same machine).

Another example, at one stage, the ordinary Array implementation in most browsers was counterintuitively faster than the TypedArray implementation.

And then consider this recent Chromium issue: http://code.google.com/p/chromium/issues/detail?id=123228 where Chrome's WebSocket client implementation takes 160ms to transfer 1mb from a localhost server.

Does anyone know if there is a website that compares browser performance across these api's, continuously updated as new browser versions are released? It would be great to a have a single page that shows:

1. A subset of the LevelDB benchmark applied to IndexedDB in Chrome and Firefox where possible (and compared to the same operations against Kyoto Cabinet and raw LevelDB).

2. Time to allocate a 1mb, 10mb, 100mb, 1gb TypeArray, and timings for standard operations on these.

3. WebSocket transfer speeds and browser memory usage, for binary data with 1mb, 10mb, 100mb, 1gb message sizes (and compared to the fastest non-browser WebSocket clients).

4. Browser storage limits, and permissions policies, and which browsers allow the user to grant privileges without going through a proprietary webstore.

Something like that would give more power to the next generation of web apps.