I'm just trying to understand how you've set this up with the prefix. Are you just appending the prefix to the beginning of your subsequent regex? I can't make that work. With the prefix it doesn't replace anything. Without the prefix it replaces inside the tag attributes (which is what I'm trying to avoid).

Here's my attempt:

prefix = "(?![^<]*</(?i)(?:textarea|script|style)(?i)\W)(?|^|\\G)[^<]*?)(?<!&(?:[a-zA-Z][a-zA-Z0-9]{0,25}|##[0-9]{0,25}))";

str = "some html code";

regex = "e";
replaceWith = "3″;

result = str.replace(prefix & regex, replaceWith);

Any advice?