Javascript String lastIndexOf(s, fromIndex)

String.prototype.lastIndexOf(s, fromIndex) {
  if (!fromIndex) {
    fromIndex = this.length - 1;/*  w  ww.ja  va  2  s  .c om*/
  }
  
  var idx = -1;
  for (var i = fromIndex; i >= 0; i--) {
    var matches = true;
    for (var j = s.length, len2 = s.length; j >= 0; j--) {
      if (this[i - len2 + j] != s[j]) {
        matches = false;
        break;
      }
    }
    if (matches) {
      idx = i;
      break;
    }
  }
  
  return idx;
};