var sum1 = prompt("请输入第一个数字") * 1;
var sum2 = prompt("请输入第二个数字") * 1;
var sum = sum1 + sum2;
console.log("两者之间的和为" + sum);
<html>
<head>
<meta charset="utf-8">
<body>
<script src="./ch05-2.js"></script>
</body>
</head>
</html>


