数组去重复数字的方法

<script type="text/javascript">

Array.prototype.distinct = function() {
  var x = [], r = [];
  for(var i = 0; i < this.length; i++) {
    x['_' + this[i]] = this[i];
  }
  for(var b in x) {
    if(typeof x[b] != 'function') {
      alert(typeof b);
      r.push(x[b]);
    }
  }
  return r;
}

window.onload = function() {
  var a = [ 1, 4, 2, 4, 3, 8, 10, 3, 9, 1, 9, 7, 111 ];
  var r = a.distinct();
  alert(a.join(','));
  alert(r.join(','));
}
</script>

原来数组的下标识可以是字符串