<script type="text/javascript">
function count(){
var=a,b,c,result;
a=document.getElementById('txt1').value;
b=document.getElementById('txt2').value;
c=document.getElementById('select').value;
switch(c):
{
case "+":result=parseInt(a)+parseInt(b);break;
case "-":result=parseInt(a)-parseInt(b);break;
case "*":result=parseInt(a)*parseInt(b);break;
case "/":result=parseInt(a)/parseInt(b);break;
}
document.getElementById('fruit').value=result;
}
</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>
三个问题，声明多变量时
var result，
a=document.getElementById('txt1').value;
b=document.getElementById('txt2').value;
c=document.getElementById('select').value;
-----------------------------------------------------------
switch 语句中没有冒号
switch() {
}
------------------------------------------------------------
onclick=count() 不要加引号
switch的每一个case后面有break；配套