Converting php regexp to javascript regexp

Question

I need some help converting this PHP regular expression to a Javascript one though I am not very familiar to regular expressions:

$regex = "((https?|ftp)\:\/\/)?"; // SCHEME
$regex .= "([a-z0-9+!*(),;?&=\$_.-]+(\:[a-z0-9+!*(),;?&=\$_.-]+)?@)?"; // User and Pass
$regex .= "([a-z0-9-.]*)\.([a-z]{2,3})"; // Host or IP
$regex .= "(\:[0-9]{2,5})?"; // Port
$regex .= "(\/([a-z0-9+\$_-]\.?)+)*\/?"; // Path
$regex .= "(\?[a-z+&\$_.-][a-z0-9;:@&%=+\/\$_.-]*)?"; // GET Query
$regex .= "(#[a-z_.-][a-z0-9+\$_.-]*)?"; // Anchor

Possible duplicate of http://stackoverflow.com/questions/9309349/convert-php-regex-to-javascript-regex — Xavier, Jun 29 '13 at 15:34
*sigh* why yes? just because there are similar keywords in the question it doesn't mean it covers it. — Karoly Horvath, Jun 29 '13 at 15:36
it seems like you could do the same thing in javascript. if you just stuff everything into a single line, wrap it in `/.../`, that should work fine. if you want to keep the string concatenation, you need to double all backslashes, and then do `var r = new RegExp(regexString);` — Martin Ender, Jun 29 '13 at 15:39
[this seems easier](http://james.padolsey.com/javascript/parsing-urls-with-the-dom/) — Wrikken, Jun 29 '13 at 15:43

score 3 · Accepted Answer · answered Jun 29 '13 at 15:50

While the others are correct, that using some other means to parse the function would be easier, here is how you can convert the regex.

The regex contains no advanced constructs which are not available in JavaScript or have a different meaning. Hence, you can simply use the same expression in a regex literal:

var r = /((https?|ftp)\:\/\/)?([a-z0-9+!*(),;?&=\$_.-]+(\:[a-z0-9+!*(),;?&=\$_.-]+)?@)?([a-z0-9-.]*)\.([a-z]{2,3})(\:[0-9]{2,5})?(\/([a-z0-9+\$_-]\.?)+)*\/?(\?[a-z+&\$_.-][a-z0-9;:@&%=+\/\$_.-]*)?(#[a-z_.-][a-z0-9+\$_.-]*)?/;

Now regex literals don't support concatenation, and neither does JS have the x modifier which would allow you to split the expression of multiple lines. So if you want to keep the pattern in multiple parts, to comment it, you'll have to concatenate a string again and pass that string to the RegExp constructor. The catch here is that backslashes need to be doubled, because JavaScripts string compilation will swallow up each unescaped backslash (so you need to escape the backslashes for them to reach the regex engine):

var rString = "((https?|ftp)\\:\\/\\/)?"; // SCHEME
rString += "([a-z0-9+!*(),;?&=\\$_.-]+(\\:[a-z0-9+!*(),;?&=\\$_.-]+)?@)?"; // User and Pass
rString += "([a-z0-9-.]*)\\.([a-z]{2,3})"; // Host or IP
rString += "(\\:[0-9]{2,5})?"; // Port
rString += "(\\/([a-z0-9+\\$_-]\\.?)+)*\\/?"; // Path
rString += "(\\?[a-z+&\\$_.-][a-z0-9;:@&%=+\\/\\$_.-]*)?"; // GET Query
rString += "(#[a-z_.-][a-z0-9+\\$_.-]*)?"; // Anchor
var r = new RegExp(rString);

In any case, r can now be used with your favourite matching function (match on a string, or test or exec on r).

Converting php regexp to javascript regexp

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