Just In Time

there are no more javascript interpreter

JavaScriptCore Nitro

Webkit / Safari

Compiles JavaScript to native machine code since 2008, just in time.

JägerMonkey

Firefox 4+

Based on JavaScriptCore Nitro.

V8

Chromium / Google Chrome 1+

Just in time compiling, one month later than Webkit.

Chakra

Internet Explorer 9+

Yes, Internet Explorer also does. And some fancy multi core stuff.

So, modern Javascript engines never interpret javascript?

Nope, they do. While compiling, they are interpreting the byte code, line for line. The result is that javascript applications speed up when the compiling is done. For video games based on javascript it would be nice to start after compiling to get stable fps.
I am searching for a way to do that, we will see.