Question

I’m writing a regular expression in javascript that replaces whitespaces except when:

1. Some specific syntax is in front of the whitespace
2. It’s surrounded in both single as double quotes (escaped quotes within quotes excluded)

Now, I’ve got a big part working. It matches all patterns that doesn’t have the specific syntax in front of the whitespace, however, I’m stuck with the quote part.

return str.replace(/(function|new|return|var)?\s/g, function($0, $1) {
    return $1 ? $0 : '';
});

I’ve done quite some testing, but I just can’t figure it out. Thanks in advance.

Answer 1

You can use:

var str = "foo  \"b a \\\" r\" new y 'l o l' foo lol; var x = new 'fo \\' o' ";

var result = str.replace(/(function|new|return|var)?\s+(?=(?:[^\\"']|\\.)*(?:(?:"(?:[^\\"]|\\.)*"|'(?:[^\\']|\\.)*'))*(?:[^\\"']|\\.)*$)/gm,
function($0, $1) { return $1 ? $0 : ''; });

See http://jsfiddle.net/qCeC4/

Lookahead part in Perl /x form:

s/
\s+
(?=
    (?:[^\\"']|\\.)*
    (?:
        (?:
            "(?:[^\\"]|\\.)*"
            |
            '(?:[^\\']|\\.)*'
        )
    )*
    (?:[^\\"']|\\.)*$
)
//xmg;

Note: As I said before, this is not a good way to parse JS, and will break on comments, regex quoting, and who knows what else.

Note2: Forgot to add that this only works for “valid” quoting, all quotes must be closed.