The following regex code to remove comments from a JavaScript chunk of code was developed with the help of several awesome Perl monks at this site...

The Code

#---------------------------------------------------------------------
+-
# Here is the fundamental code to match JavaScript code.
# This includes regular expressions and quoted strings.
#---------------------------------------------------------------------
+-
my ($regexJSCode) = qr{
    # First, we'll list things we want 
    # to match, but not throw away

    (?: 
        # Match a regular expression (they start with ( or =).
        # Then the have a slash, and end with a slash.
        # The first slash must not be followed by * and cannot contain
        # newline chars. eg: var "re = /\*/;" or "a = b.match (/x/);"
    
        [\(=] \s*
        /
        (?:
            # char class contents
            \[ \^? ]? (?: [^]\\]+ | \\. )* ]
            |
            # escaped and regular chars (\/ and \.)
            (?: [^[\\\/]+ | \\. )*
        )*
        /
        (?:
            [gi]*
            # next characters are not word characters
            (?= [^\w] )
        )
    ) 

    | # or double quoted string
    (?: 
        "[^"\\]* (?:\\.[^"\\]*)*" [^"'/]* 
    )+  

    | # or single quoted constant
    (?: 
        '[^'\\]* (?:\\.[^'\\]*)*' [^"'/]* 
    )+  
}x;

#---------------------------------------------------------------------
+-
# Here is the fundamental code to match JavaScript comments and commen
+t blocks.
#---------------------------------------------------------------------
+-
my ($regexJSComments) = qr{
    # or we'll match a comment. Since it's not in the
    # $1 parentheses above, the comments will disappear
    # when we use $1 as the replacement text.

    / # (all comments start with a slash)
    (?:    
        # traditional C comments
        (?: 
            \* [^*]* \*+ 
            (?: [^/*] [^*]* \*+ )* 
            / 
        )

        | # or C++ //-style comments
        (?: 
            / [^\n]*
        )
    )
}x;

#---------------------------------------------------------------------
+-
# Get rid of all comments from the string.
#---------------------------------------------------------------------
+-
$strOutput =~ s{    
    ( $regexJSCode ) | $regexJSComments
}{$1}gsx;
[download]

Input (Problems)

function test (str) {
    // A comment.
    alert ("test");    

    var reForwardSlash = /\//;
    var reBackslash = /\\/;
    
    if (str.match(regexForwardslash) && str.match(regexBackslash)) {
        return true;
    }

}
[download]

Parsed Output (Incorrect)

The choking occurs on the regexForwardSlash variable:

function test (str) {
        alert ("test");
        var reForwardSlash = /\
        var reBackslash = /\\/;
        if (str.match(regexForwardslash) && str.match(regexBackslash))
+ {
                return true;
        }
}
[download]

If we get rid of the alert ("test") string, we will get the proper parsing... so the regex we have developed has some issues... Here's a successful parse with the same regex, just different input.

Input (No Problems)

function test (str) {
    // A comment.

    var reForwardSlash = /\//;
    var reBackslash = /\\/;
    
    if (str.match(regexForwardslash) && str.match(regexBackslash)) {
        return true;
    }

}
[download]

Parsed Output (Correct)

This is the expected parse output.

function test (str) {
        var reForwardSlash = /\//;
        var reBackslash = /\\/;
        if (str.match(regexForwardslash) && str.match(regexBackslash))
+ {
                return true;
        }
}
[download]

Help Wanted

So as you can see, I'm doing something wrong in the regex... Does anyone see what the problem is? Any help is greatly appreciated.

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