Making links clickable in Javascript?

Question

Is there an simple way of turning a string from

Then go to http:/example.com/ and foo the bar!

into

Then go to <a href="http://example.com">example.com</a> and foo the bar!

in Javascript within an existing HTML page?

Answer 1

Yes. The simplest way is to use a regular expressions to substitute things that look like a link for their linked equivalents. Something like:

node.innerHTML = node.innerHTML.replace(/(http:\/\/[^\s]+)/g, "<a href='$1'>$1</a>")

(my RegEx is a little rusty, so you may need to play with the syntax). This is just a simple case. You need to be wary of script injection here (for example if I have http://"><script>doevil()</script>). One way to work around this is by using a link building function:

node.innerHTML = node.innerHTML.replace(/ ... /g, buildLink($1));

Where buildLink() can check to make sure the URL doesn't contain anything malicious.

However, the RegEx-innerHTML method will not perform very well on large bodies of text though, since it tears down and rebuilds the entire HTML content of the node. You can achieve this with DOM methods as well:

• Find reference to the text node
• In the content, find start and end indexes of a URL
• Use splitText() method to split the node into 3: before, link, after
• Create an <a> node with the href that's the same as the link
• Use insertBefore() to insert this <a> node before the link
• Use appendChild() to move the link into the <a> node

Answer 2

First, "within an HTML page" is difficult because a "page" is actually a DOM tree (which is partially composed of text nodes and mostly composed of HTML elements).

The easiest way to approach this problem would be to target content-rich text nodes. For each text node, apply something like this:

// we'll assume this is the string of a content-rich text node
var textNode = document.getElementById('contentNode');
textNode.innerHTML = textNode.innerHTML.replace(/(\s)(http:\/\/[^\s]+)(\s)/g, '$1<a href="$2">$2</a>$3');

BTW: there are security implications here. If you generate links from unsterilized text, there is the possibility of XSS.