<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var txt1=parseInt(document.getElementById("txt1").value);
var txt2=parseInt(document.getElementById("txt2").value);
var sel=document.getElementById("select").value;
var fruit=document.getElementById("fruit").value;
var result="";
switch(sel)
{
case "+":
result=txt1+txt2;
break;
case "-":
result=txt1-txt2;
break;
case "*":
result=txt1*txt2;
break;
case "/":
result=txt1/txt2;
break;
}
fruit=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()" />
<input type='text' id='fruit' />
</body>
</html>
为什么没有输入结果？
fruit=result;把这个代码改成document.getElementById("fruit").value = result就可以了
因为你这种写法是给变量fruit重新赋值而不是给id为fruit的元素赋值，所以不对