Detect URLs in text with JavaScript

Does anyone have suggestions for detecting URLs in a set of strings?

arrayOfStrings.forEach(function(string){
  // detect URLs in strings and do something swell,
  // like creating elements with links.
});

Update: I wound up using this regex for link detection… Apparently several years later.

kLINK_DETECTION_REGEX = /(([a-z]+://)?(([a-z0-9-]+.)+([a-z]{2}|aero|arpa|biz|com|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel|local|internal))(:[0-9]{1,5})?(/[a-z0-9_-.~]+)*(/([a-z0-9_-.]*)(?[a-z0-9+_-.%=&]*)?)?(#[a-zA-Z0-9!$&'()*+.=-_~:@/?]*)?)(s+|$)/gi

The full helper (with optional Handlebars support) is at gist #1654670.

Answer

First you need a good regex that matches urls. This is hard to do. See here, here and here:

…almost anything is a valid URL. There are some punctuation rules for splitting it up. Absent any punctuation, you still have a valid URL.

Check the RFC carefully and see if you can construct an “invalid” URL. The rules are very flexible.

For example ::::: is a valid URL. The path is ":::::". A pretty stupid filename, but a valid filename.

Also, ///// is a valid URL. The netloc (“hostname”) is "". The path is "///". Again, stupid. Also valid. This URL normalizes to "///" which is the equivalent.

Something like "bad://///worse/////" is perfectly valid. Dumb but valid.

Anyway, this answer is not meant to give you the best regex but rather a proof of how to do the string wrapping inside the text, with JavaScript.

OK so lets just use this one: /(https?://[^s]+)/g

Again, this is a bad regex. It will have many false positives. However it’s good enough for this example.

function urlify(text) {
  var urlRegex = /(https?://[^s]+)/g;
  return text.replace(urlRegex, function(url) {
    return '<a href="' + url + '">' + url + '</a>';
  })
  // or alternatively
  // return text.replace(urlRegex, '<a href="$1">$1</a>')
}

var text = 'Find me at http://www.example.com and also at http://stackoverflow.com';
var html = urlify(text);

console.log(html)
// html now looks like:
// "Find me at <a href="http://www.example.com">http://www.example.com</a> and also at <a href="http://stackoverflow.com">http://stackoverflow.com</a>"

So in sum try:

$$('#pad dl dd').each(function(element) {
    element.innerHTML = urlify(element.innerHTML);
});