<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count()
{
var d = "";
var a= document.getElementById("txt1").value;
var b= document.getElementById("txt2").value;
var c= document.getElementById("select").value;
switch(c)
{
case "+":
d = parseInt(a)+parseInt(b);
break;
case "-":
d = a-b;
break;
case "*":
d = a*b;
break;
default:
d = a/b;
}
document.getElementById({"fruit").value = d ;
}
</script>
</head>
<body>
<input type='text' id='txt1' />
<select id='select'>
<option value='+'>+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type='text' id='txt2' />
<input type='button' value=' = ' onclick="count()" /> <!--通过 = 按钮来调用创建的函数，得到结果-->
<input type='text' id='fruit' />
</body>
</html>
function count(){
var num1=parseFloat(document.getElementById("txt1").value);
var num2=parseFloat(document.getElementById("txt2").value);
var result=document.getElementById("fruit");
var op=document.getElementById("select").value;
switch(op){
case'+':result.value=num1+num2;break;
case'-':result.value=num1-num2;break;
case'*':result.value=num1*num2;break;
case'/':result.value=num1/num2;break;
}这样是不是简洁点。
找到问题了，是代码多写了一个{，document.getElementById({"fruit").value = d ;