js 动态添加 事件

<button id="test42">test42</button>
  <script>
  function DoClick()
  {   
    alert('calling DoClick');   
  }
  function AttClick1()
  {
    alert('calling AttClick1');
  }
   function AttClick2()
  {
    alert('calling AttClick2');
  }
  function AttClick3()
  {
    alert('calling AttClick3');
  }
  var td_value=document.getElementById("test42");
  
    if(window.addEventListener){ // Mozilla, Netscape, Firefox 
        td_value.addEventListener('click', AttClick2, false); 
        td_value.addEventListener('click', AttClick3, false); 
        td_value.addEventListener('click', DoClick, false); 
        td_value.addEventListener('click', AttClick1, false); 
    } else { // IE 
        td_value.attachEvent('onclick',  function(){alert('21');}); 
        td_value.attachEvent('onclick',  function(){alert('22');}); 
    } 
 
  </script>