Using regular expressions to find img tags without an alt attribute

Question

I am going through a large website (1600+ pages) to make it pass Priority 1 W3C WAI. As a result, things like image tags need to have alt attributes.

What would be the

Answer 1

Here is what I just tried in my own environment with a massive enterprise code base with some good success (found no false positives but definitely found valid cases):

]*\balt=)[^>]*?>

What's going on in this search:

1. find the opening of the tag
2. look for the absence of zero or more characters that are not the closing bracket while also …
3. Checking for the absence of of a word that begins with "alt" ("\b" is there for making sure we don't get a mid-word name match on something like a class value) and is followed by "=", then …
4. look for zero or more characters that are not the closing bracket
5. find the closing bracket

So this will match:

But it won't match either of these: