Regex Engines in JavaScript

proggit led me to this post by what appears to be a member of Google’s Chrome team, regarding the Squirrelfish Extreme engine’s performance on regex. There’s some fascinating stuff here, including the following gem:

WREC doesn’t save the intermediate matches, it just keeps track of the length of the text matched against /a*/ (repeatCount in my code) and decrements the position and count in order to backtrack. This is great, because it uses only two words of memory for state (instead of N million) but can find the next longest match very quickly (just 4 instructions).

If you’ve never read Mastering Regular Expressions, by Jeff Friedl, you might have trouble following some of the underlying concepts, but you should go out and pick up a copy today