JS动态添加事件

var t = document.getElementById("tab1");  
t.onclick = function tst(){  
    alert('');  
} 

var tb = document.getElementById("tab1");  
 if(window.addEventListener){ // Mozilla, Netscape, Firefox  
     td_value.addEventListener('click', alert('11'), false);  
     td_value.addEventListener('click', alert('12'), false);  
 } else { // IE  
     td_value.attachEvent('onclick',  function(){alert('21');});  
     td_value.attachEvent('onclick',  function(){alert('2'2);});  
 }