javascript 批改disabled值

javascript 修改disabled值
错误的如下:

function showCardNum(index)
		{
			var cardOrderDt=document.getElementById("cardOrderDt_"+index);
			if(cardOrderDt.disabled=="disabled")
			{
				cardOrderDt.disabled="";
			}
			else
			{
				cardOrderDt.disabled="disabled";
			}
		}

正确的如下

function showCardNum(index)
		{
			var cardOrderDt=document.getElementById("cardOrderDt_"+index);
			if(cardOrderDt.disabled==true)
			{
				cardOrderDt.disabled=false;
			}
			else
			{
				cardOrderDt.disabled=true;
			}
		}

虽然在html表单域上，是以disabled="disabled"的形式，但是要用javascript改变它们的话，不再是字符串了，而是布尔值。即disabled=true或false