Find Matching String in Javascript and adorning it with span and class

gistfile1.txt

/*
 * Taken from https://github.com/ghiden/angucomplete-alt/blob/master/angucomplete-alt.js
 */
function findMatchString(target, str) {
  var result, matches, re;
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
  // Escape user input to be treated as a literal string within a regular expression
  re = new RegExp(str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'), 'i');
  if (!target) { return; }
  matches = target.match(re);
  if (matches) {
    result = target.replace(re,
        '<span class="'+ scope.matchClass +'">'+ matches[0] +'</span>');
  }
  else {
    result = target;
  }
  return $sce.trustAsHtml(result);
}