Regex Invalid Group

Question

Can anyone see why this is giving an Invalid regular expression: Invalid group error?

text.replace(/(?<!br|p|\/p|b|\/b)>/g, "&gt;");

This one is OK:

text.replace(/<(?!br|p|\/p|b|\/b)/g, "&lt;");

So, I'm not sure where I'm going wrong with the first one (>).

Here's a fiddle with an example.

Answer 1

JavaScript does not support lookbehinds. Here is one way you can get the same behavior:

text = text.replace(/(br|p|\/p|b|\/b)?>/g, function($0, $1){
    return $1 ? $0 : ">";
});

This approach comes from the following blog entry: Mimicking Lookbehind in JavaScript

Here is an updated fiddle.