Manpages - JavaScript_Minifier_XS.3pm

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JavaScript::Minifier::XS - XS based JavaScript minifier


use JavaScript::Minifier::XS qw(minify); my $js = …; my $minified = minify($js);


JavaScript::Minifier::XS is a JavaScript minifier; its designed to remove unnecessary whitespace and comments from JavaScript files, which also not breaking the JavaScript.

JavaScript::Minifier::XS is similar in function to JavaScript::Minifier, but is substantially faster as its written in XS and not just pure Perl.


Minifies the given $js, returning the minified JavaScript back to the caller.


JavaScript::Minifier::XS minifies the JavaScript by removing unnecessary whitespace from JavaScript documents. Comments (both block and line) are also removed, except when (a) they contain the word copyright in them, or (b) they’re needed to implement IE Conditional Compilation.

Internally, the minification process is done by taking multiple passes through the JavaScript document:

Pass 1: Tokenize

First, we go through and parse the JavaScript document into a series of tokens internally. The tokenizing process does not check to make sure you’ve got syntactically valid JavaScript, it just breaks up the text into a stream of tokens suitable for processing by the subsequent stages.

Pass 2: Collapse

We then march through the token list and collapse certain tokens down to their smallest possible representation. If they’re still included in the final results we only want to include them at their shortest.

Runs of multiple whitespace characters are reduced down to a single whitespace character. If the whitespace contains any end of line (EOL) characters, then the end result is the first EOL character encountered. Otherwise, the result is the first whitespace character in the run.

Pass 3: Pruning

We then go back through the token list and prune and remove unnecessary tokens.

Wherever possible, whitespace is removed; before+after comment blocks, and before+after various symbols/sigils.
Comments that are either (a) IE conditional compilation comments, or that (b) contain the word copyright in them are preserved. All other comments (line and block) are removed.
Everything else
We keep everything else; identifiers, quoted literal strings, symbols/sigils, etc.

Pass 4: Re-assembly

Lastly, we go back through the token list and re-assemble it all back into a single JavaScript string, which is then returned back to the caller.


Graham TerMarsch (


Copyright (C) 2007-, Graham TerMarsch. All Rights Reserved.

This is free software; you can redistribute it and/or modify it under the same license as Perl itself.



Author: dt

Created: 2022-02-20 Sun 16:21