<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
//获取第一个输入框的值
var i=document.getElementById('txt1').value;
//获取第二个输入框的值
var j=document.getElementById('txt2').value;
//获取选择框的值
var k=document.getElementById('select').value;
//获取通过下拉框来选择的值来改变加减乘除的运算法则
var sum;
switch(k){
case "+":
sum=parseInt(i)+parseInt(j);
break;
case "-":
sum=parseInt(i)-parseInt(j);
break;
case "*":
sum=parseInt(i)*parseInt(j);
break;
case "/":
sum=parseInt(i)/parseInt(j);
break;}
//设置结果输入框的值
document.getElementById("fruit").value = sum;
}
</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() />
<input type='text' id='fruit' />
</body>
</html>
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