String compression in JavaScript

Question

I'm looking for a JavaScript function that given a string returns a compressed (shorter) string.

I'm developing a Chrome web application that saves long strings (HTML) to a local database. For testing purposes I tried to zip the file storing the database, and it shrank by a factor of five, so I figured it would help keep the database smaller if I compressed the things it stores.

I've found an implementation of LZSS in JavaScript here: http://code.google.com/p/u-lzss/ ("U-LZSS").

It seemed to work when I tested it "by hand" with short example strings (decode === encode), and it's reasonably fast too, in Chrome. But when given big strings (100 ko) it seems to garble/mix up the last half of the string.

Is it possible that U-LZSS expects short strings and can't deal with larger strings? And would it be possible to adjust some parameters in order to move that upper limit?

Answer 1

I just released a small LZW implementation especially tailored for this very purpose as none of the existing implementations did meet my needs.

• Here is the home page of the project

• Here is a link to a demo comparing it with LZMA level 1

That's what I'm using going forward, and I will probably try to improve the library at some point.