[courage]

The time required to JIT compile code apparently has a big effect on web browser JavaScript performance. Web pages often have a lot of cold code that isn't run often.

JavaScriptCore is getting a new fast interpreter that will be the first choice way to run code that hasn't proven hot: http://trac.webkit.org/changeset/108309

[justincormack]

Well there certainly is a lot of scope to make a faster interpreter, as eg according to http://news.ycombinator.com/item?id=1187901 the Luajit interpreter is faster than compiled v8...

[cygx]

I'd be surprised if that's still true today. V8 used to be consistently slower than LuaJIT, but has caught up since then.