如何添加DOM 0级事件
<script type="text/javascript">
function count(){
var txt1 = parseFloat(document.getElementById("txt1").value);
var txt2 = parseFloat(document.getElementById("txt2").value);
var select = document.getElementById("select").value;
var s
switch(select)
{
case "+":
s=txt1+txt2;
break;
case "-":
s=txt1-txt2;
break;
case "*":
s=txt1*txt2;
break;
case "/":
s=txt1/txt2;
break;
}
document.getElementById("fruit").value = s;
}
var btn = document.getElementById("btn").value;
btn.onclick = count;
</script>在这里应该如何给按钮添加DOM 0级事件
