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I'm trying to enter a javascript competition where the script has to be <= 1kb in size. Minifying and eval is allowed, so I've run it through google's closure compiler (which does slightly better than any others I've tried).

But I've found that if I convert the script to a string, and replace long words like 'function' and 'return' with single chars, I can reduce that even further. Then, by embedding the string in my script, performing the substitution to restore it, and then 'evaling' it, I can get the original behaviour.

So I was wondering if I could generalise this last method. Has anyone seen or written code to compress/decompress strings in this way? Feel like thinking about it?

EDIT To make myslelf clear, I'm asking about compressing and decompressing strings in javascript - not minifying. E.g. how to find the most common patterns in a string, and how to write a tiny decompressor in javascript for strings where these occurences have been replaced with single chars.

Thanks.

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    Erm... maybe Dean Edward's /packer/? Commented Aug 15, 2010 at 4:01
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    compressorrater.thruhere.net - a helpful tool for comparing output from different minifiers or compression methods Commented Aug 15, 2010 at 4:10
  • None of the minifiers I've tried work as well as Google's (including packer), which I'm already using. The question is about compressing/decompressing strings - it just happens that my string is minified js. Commented Aug 16, 2010 at 2:29
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    maybe you've already read these, but here are two recent articles from A List Apart on how to write code that minifiers can compress more easily: alistapart.com/articles/better-javascript-minification alistapart.com/articles/javascript-minification-part-II Commented Aug 18, 2010 at 13:37
  • @Jenni - cheers, I will read that. I actually got my script down to an acceptable size. But I'm still interested in this idea of compressing/decompressing inside the script. Commented Aug 18, 2010 at 13:54

3 Answers 3

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Do you happen to be looking for http://www.iteral.com/jscrush/ ? I found it useful for the same competition (I assume it is js1k).

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2 Comments

Nope. That's another minifier. I'm looking to compress and decompress strings.
Apologies. That's exactly the sort of thing I was talking about.
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Have you considered shortening your code by creating a shortcut for those JavaScript objects and methods that you use a lot in your code:

var d = document; var id = d.getElementById;

And then instead of writing

document.getElementById("foo")

You can write

id("foo");
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Yep, done that already...but also, the closure compiler does it as part of it's optimisation as well.
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Tokenisation is the preferred method for compressing scripts as it works with the individual keywords and other names.

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Most of this is done by the closure compiler - there are very few javascript keywords I'm using (function, return etc) but the closure compiler automatically makes all function names just 1 letter long, etc.

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