JavaScript negative lookbehind issue

Question

I\'ve got some JavaScript that looks for Amazon ASINs within an Amazon link, for example

http://www.amazon.com/dp         


        

Answer 1

You need to use a lookahead to filter the /e/* ones out. Then trim the leading /e/ from each of the matches.

var source; // the source you're matching against the RegExp
var matches = source.match(/(?!\/e)..\/[A-Z0-9]{10}/g) || [];
var ids = matches.map(function (match) {
  return match.substr(3);
});

Answer 2

In your case an expression like this would work:

/(?!\/e)..\/([A-Z0-9]{10})/

Answer 3

([A-Z0-9]{10}) will work equally well on the reverse of its input, so you can

1. reverse the string,
2. use positive lookahead,
3. reverse it back.