javascript regex to parse urls without protocol

Question

String.prototype.linkify = function() {
this.replace(/((ht|f)tp:\/\/)?([^:\/\s]+)\w+.(com|net|org)/gi, '<a href="$&">$&</a>')
}

with http://www.google.com http://yahoo.com www.facebook.com it matches them all, however I want facebook to be prepended with the protocol group if it does not exist. Is there a way to do this without doing two .replace ?

Daniel Brockman · Accepted Answer · 2011-09-26 19:12:15Z

1

I would do something like this:

String.prototype.linkify = function () {
  return this.replace(/((?:ht|f)tp:\/\/)?([^:\/\s]+\w+\.(?:com|net|org))/gi, function (_, protocol, rest) {
    var url = (protocol || "http://") + rest
    return '<a href="' + url + '">' + url + '</a>'
  })
}

(I fixed a couple of other problems with your code: you were missing a return and you were matching the domain name period using . rather than \..)

And I assume I don’t need to point out how poorly this will match URL:s in general, due to a number of problems with your pattern.

answered Sep 26, 2011 at 19:12

Daniel Brockman

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2 Comments

Tom Fobear Over a year ago

:how would your regex go? also, can you explain the parameters in the anonymous function in replace?

Daniel Brockman Over a year ago

The parameters are simply $&, $1, $2. My idea of a good way to match URLs in general is outside the scope of this question, since it is actually a pretty hard problem. To put it simply, though, I would start with a complete list of all TLDs, and then match stuff ending in a TLD and having various fluff on either side (that’s easier once you realize that you have to start from the TLD).

lunixbochs · Accepted Answer · 2011-09-26 19:06:25Z

1

If you don't actually need to match FTP URLs, you can just assume the "http://" section of the link. This regex does that, while allowing you to also use https.

this.replace(/(http(s)?:\/\/)?(([^:\/\s]+)\.(com|net|org))/gi,
                         '<a href="http$2://$3">http$2://$3</a>')

I'm not sure what your use case is, but I'd like to note this regex will fail on the following urls:

http://google.com/spam = <a href="http://google.com">http://google.com</a>/spam
http://google.ca = no match

This is because you're using few hardcoded tlds (com, net, org), and aren't matching any characters after the domain.

answered Sep 26, 2011 at 19:06

lunixbochs

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1 Comment

Asmor Over a year ago

Clever solution to making sure to grab https as appropriate.

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