IconVault's JS Benchmark settles arguments about fast code: paste in multiple JavaScript snippets, and it races them against each other, measuring operations per second for each. The live results table shows the winner and how many times faster it is than the rest.

Snippets run in a sandboxed new Function environment in your own browser, nothing is uploaded, and you can name, edit, and re-run snippets freely. Honest note: results measure your machine and browser, so use them for relative comparison, not absolute claims. Free and runs fully in your browser.