select不管怎么选值不变

<select name="" id="mm" onfocus="this.defaultIndex=this.selectedIndex;" onchange="this.selectedIndex=this.defaultIndex;">

    <option value="">sf</option>

      <option value="">s435ff</option>

        <option value="">ssff</option>

          <option value="">sfxcv</option>

</select>

select不管怎么选值不变

原文：http://10992653.blog.51cto.com/10982653/1772065