计算器

<!--计算器类型 number-->
<form>
<input type="number" id="num1">
+
<input type="number" id="num2">
=
<input type="number" id="result" readonly>
<input type="button" value="结果是" onclick="sum()">
</form>

<script>
function sum(){
var n1= document.getElementById("num1").valueAsNumber;
var n2= document.getElementById("num2").valueAsNumber;
document.getElementById("result").valueAsNumber=n1+n2;
}
</script>