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I am combining all my javascriupt into one neat file in order to lower http requests! Im stuck removing the comments /* comments */ and // comments. My level is by far below minification or parsing stuff. I know how to make macaroni strings. Anything more complex than that, you will not find in my computer or kitchen, SO:

QUESTION

meanwhile at combining it to one file, i want to remove all comments.
What is the correct regex for this?

<?php
header('Content-type: text/javascript');    
$offset = 60 * 60 * 24; // Cache for a day
header ('Cache-Control: max-age=' . $offset . ', must-revalidate');
header ('Expires: ' . gmdate ("D, d M Y H:i:s", time() + $offset) . ' GMT');

ob_start("compress");
function compress($buffer) {

# NOT SURE, not all new lines are removed??
# remove tabs, spaces, newlines, etc.
$buffer = str_replace(array("\r\n", "\r", "\t", '  ', '    '), '', $buffer);  

# WORKS !!!
# remove comments / XXXXXXX
$buffer = preg_replace('(// .+)', '', $buffer);

######################################################################## 
# !! STUCK HERE !! OUTPUT FILE LOOKS OK BUT WEBSITE DOESNT LOAD OK IF THIS IS ON
# remove comments / * XXX  (enters etc) XXXX  * /
# $buffer = preg_replace('#/\*(?:.(?!/)|[^\*](?=/)|(?<!\*)/)*\*/#s', '', $buffer);
########################################################################        

return $buffer;
}

include('../file1.js');
include('../file2.js');  
ob_end_flush();
?>

It would be great if it would catch and delete the following:

/* XXXX */

/* 
  XXXX
  XXXX
*/

Thats all! Cant get it to work nomatter what regex i use even with this incredible tool, where i FOUND the right match to be:

RegExp: /\/\*(?:.(?!/)|[^\*](?=/)|(?<!\*)/)*\*\//gs
pattern: \/\*(?:.(?!/)|[^\*](?=/)|(?<!\*)/)*\*\/
flags: gs

http://gskinner.com/RegExr/

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2 Answers

up vote 4 down vote accepted

Using regular expressions isn't the most efficient way of removing Javascript comments. You need a string parser and minifier. See http://razorsharpcode.blogspot.com/2010/02/lightweight-javascript-and-css.html

If you insist on regex patterns, think about how you would parse this simple code that contains no Javascript comments at all:

var regex=/(ftp|http|https):\/\//; alert('hello, world'); return regex;

Notice the double slash before alert(). A stupid parser that uses regular expressions will treat valid Javascript code as comments!

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1  
I second this suggestion; @Sam: If you're trying to optimize your responses, you should really consider using minifiers in place of custom comment removers. Google Closure Compiler, YUI Compressor or Uglify JS should be your go-to tools. – Krof Drakula Dec 10 '10 at 7:31
Thanks folks, but OMG that looks scary difficult! My main goal was to reduce HTTp request. Meanwhile at it i thought why not reduce the comments. Thats really OKA for me for now, for real. I value now not the most perfect/fastest, but something i understand and can grow with – Sam Dec 10 '10 at 8:40
2  
@Sam: Usually I am a major advocate of regexp, but comments are overly complex to remove from javascript, definitely a job for a minimizing parser. – Orbling Dec 10 '10 at 15:03
Thanks all, ive changed my question! – Sam Dec 10 '10 at 17:16
up vote 0 down vote

I hit a scenario where I load javascript code over the network via xhr, and need to clean the code for eval'ing. I'm using this code:

var cleanCode = function cleanCode(input) {
  // Remove special characters:
  return input.replace(/\/\/[^"'].*?\n/g, '') /* //comments, but ignore a "//" if there is a quote after it */
              .replace(/\n/g, '')             /* Leftover newlines */
              .replace(/\r/g, '');            /* Carriage returns  */
};

I tested using this and the only snag I had was a comment like:

//'key': 'value'

So I had to change that code to the inline comment:

/*'key': 'value'*/ //LEAVE as inline comment, please

This code doesn't get altered:

url += '//' + ...

Feel free to edit/suggest edits to make this more readable.

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1  
This method is highly unreliable, because it relies on the assumption that // is always the beginning of a comment. Examples of failure: "Python's division: 1 // 2" and /* foo(); // some comment */ – Rob W Dec 8 '12 at 8:48
Yes, this code is extremely fragile/non-robust/unreliable. You need to have well formatted javascript. The worst case is when you have a // style comment start with a ' or ", like: //"you dope" – Devin G Rhode Dec 8 '12 at 10:08

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