Extract substring between two strings

extract.js

String.prototype.extract = function(prefix, suffix) {
	s = this;
	var i = s.indexOf(prefix);
	if (i >= 0) {
		s = s.substring(i + prefix.length);
	}
	else {
		return '';
	}
	if (suffix) {
		i = s.indexOf(suffix);
		if (i >= 0) {
			s = s.substring(0, i);
		}
		else {
		  return '';
		}
	}
	return s;
};

What about multiple matches?

Bless your soul!

cool !

u rock