<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var a =document.getElementById("txt1").value;
var b = document.getElementById("txt2").value;
var ys = document.getElementById("select").value;
var add = "";
switch(ys) {
case "+":
add = parseFloat(a)+parseFloat(b);
break;
case "-":
add = parseFloat(a)-parseFloat(b);
break;
case "*":
add = parseFloat(a)*parseFloat(b);
break;
default:
add = parseFloat(a)/parseFloat(b);
}
document.getelementById("fruit").value = add;
}
</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>
为ID为fruit赋值时getElementsById 里面二个e要大写