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Asked: 2026-06-08T08:56:48+00:00

I have made this regular expression which does exactly what I want when I

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I have made this regular expression which does exactly what I want when I test it in e.g. RegExr:

^https?:\/\/(www\.)?(test\.yahoo\.com|sub\.yahoo\.com)?(?!([a-z0-9]+\.)?(localhost|yahoo\.com))(.*)?

However when I test it in javascript it says that the expression is invalid. After hours of debugging I found out that this expression works in javascript:

^https?:\/\/(www\.)?(test\.yahoo\.com|sub\.yahoo\.com)?(?![a-z0-9]+\.)?(localhost|yahoo\.com)(.*)?

However this doesn’t do what I want (again testing in RegExr).

Why cannot I use the first expression in javascript? And how do I fix it?

UPDATE JULY 25

Sorry for the lack of info. The way I am using the Regexp is through a jQuery extension which lets me select using regexp. The script can be seen here: http://james.padolsey.com/javascript/regex-selector-for-jquery/

The specific code I am trying to get to work is:

$('a:regex(href, ^https?:\/\/(www\.)?(test\.yahoo\.com|sub\.yahoo\.com)?(?!([a-z0-9]+\.)?(localhost|yahoo\.com))(.*)?)').live('click', function(e) {

After including the linked jQuery plugin. The text strings I am testing are:

Where it is supposed to match “http://google.dk”, “http://test.yahoo.com” and “http://sub.yahoo.com/lalala” – which it does when using RegExr but failing (invalid expression) using the jQuery plugin.

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1 Answer

  1. Editorial Team

    The first regular expression is not invalid:

    var regexp = /^https?:\/\/(www\.)?(test\.yahoo\.com|sub\.yahoo\.com)?(?!([a-z0-9]+\.)?(localhost|yahoo\.com))(.*)?/;

    works fine.

    If you want to instantiate the expression from a string, you have to double all the backslashes:

    var regexp = new RegExp("^https?:\\/\\/(www\\.)?(test\\.yahoo\\.com|sub\\.yahoo\\.com)?(?!([a-z0-9]+\\.)?(localhost|yahoo\\.com))(.*)?");

    When you start from a string, you have to account for the fact that the string constant itself uses backslashes as a quoting mechanism, so there will be two evaluations made: one as a string, and one as a regular expression.

    edit — OK I think I see the problem. That plugin you’re trying to use is simply attempting to do something that’s just not going to work, given the way that Sizzle parses selectors. In other words, the problem is not with your regular expression, it’s with the overall selector. It is not even getting far enough to parse the regular expression.

    Specifically it seems to be nested parentheses inside the regular expression. Something as simple as

    $('a:regex(href, ((abc)))')

    causes an error. You can instead do something like this:

    $('a').filter(function() {
  return /^https?:\/\/(www\.)?(test\.yahoo\.com|sub\.yahoo\.com)?(?!([a-z0-9]+\.)?(localhost|yahoo\.com))(.*)?/.test(this.href);
}).whatever( ... );
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