</ in <script> tag as part of javascript regular expression ending in <

Question

I have some HTML code with inline javascript in a <script> tag that contains a regular expression removing superflous whitespace between a > and a < character as in

<script>
[...]
output = output.replace(/>\s*</g, '><');
[...]
</script> 

This is invalid HTML (eg, according to PHPs DOMDocument->loadHTML() ), as the character sequence </ ends processing and is expected to be followed by the rest of the closing tag script> .

I have tried to escape the < as < but then the expression doesn't match anymore (tested in jsfiddle ).

A workaround is to insert something in the regular expression that doesn't actually do anything but separates the < from the / , such as

output = output.replace(/>\s*[<]/g, '><');

This works and has the expected behavior, but looks like a terrible hack.

What is the right way to escape < before / in a js regular expression?

Answer 1

If PHP's DOMDocument->loadHTML() thinks the script element ends there, I'm fairly sure it's a bug in DOMDocument->loadHTML() . Script elements end with </script> , and the content of script elements is not HTML. script elements have a much more...interesting...content model than that which the spec takes several paragraphs to explain.

Regarding issues with </ , the spec only mentions dealing with <!-- and </script> , not </ in general.

But if you have to have inline script (you wouldn't have this problem if the code were in a .js file), and you have to load it with something that apparently has a bug, your hack with the character class ( [<] rather than < ) isn't bad at all. (I doubt performance is your concern, but if it were, I think we can probably say with a fair bit of assurance that the JavaScript engine's regular expression handler is going to be able to optimize that single-character character class away.)