Replace Last Match in Regex

Question

I have an autocomplete user-tagging system that fills in usernames that come after an @ symbol. I have this problem however, where I have two users with a matching substring. For example:

Tagging @billy and @b When a user fills in the @b tag with a user named (for example) @brendan, it'll replace the @billy tag. How do I go backwards and replace only the last tag?

Edit: this is my current solution, but it feels kludgy. Is there a way to do this just with RegEx?:

function tagUser (chosenUsername) {
  var userRegex = new RegExp('(^|\\s)@([' + lastUserTag() + ']*)$', 'gi');
  var caption = $("#example").val();
  var match = caption.match(userRegex);

  var lastMatch = match[match.length - 1];
  $("#example").val(caption.replace(lastMatch, " @" + chosenUsername));
}

Answer 1

Not sure if I understood your problem entirely. However just to let you know you can use negative lookahead to replace only last matched text like this:

var str='@billy and @b';
str = str.replace(/@b\b(?!.*?@b\b)/, 'brendan');