Question

Anyone help? When I run this I get ” invalid quantifier ?<=href= “

var aHrefMatch = new RegExp("(?<=href\=")[^]+?(?=")"); 
var matchedLink = mystring.match(aHrefMatch);

But I know the regular expression is valid.

Any ideas?

Answer 1

Javascript does not support lookbehind assertions. It only supports lookahead ones. The error is produced because it assumes the ? is a quantifier for 0 or 1, but there is no element to quantify at the beginning of a subpattern (started by that ( opening parenthesis)

Also, your string seems to be missing a few backslashes, as the double quotes are not escaped there. It should produce a syntax error.

Perhaps this code could help you do what you are trying to achieve:

var match = mystring.match(/href=\"([^\"]*)\"/);
var matchedLink = match[1];