JavaScript-leaning/求和.html at master · LaderBen/JavaScript-leaning · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        window.onload = function () {
            var oNum1 = document.getElementById('num1');
            var oNum2 = document.getElementById('num2');
            var oBtn = document.getElementById('btn');

            oBtn.onclick = function () {//定义点击按钮事件的函数
                if (isNaN(oNum1) || isNaN(oNum2)) {
                    alert('输入的不是一个数字')
                } else {
                    //parseInt、parseFloat字符串转数字
                    alert(parseFloat(oNum1.value) + parseFloat(oNum2.value));
                    //alert(oNum1.value+oNum2.value);//12+5结果显示为125;
                }
            };
        };
    </script>
</head>

<body>
    <input id="num1" type="text" />
    <input id="num2" type="text" />
    <input id="btn" type="button" value="sum" />

</body>

</html>