JS——制作简单的网页计算器

用JS做了一个简易的网页计算器
<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>计算器</title>

    <script type="text/javascript">

        window.onload = function () {

            var oInput01 = document.getElementById('input01');

            var oInput02 = document.getElementById('input02');

            var oFuhao = document.getElementById('fuhao');

            var oBtn = document.getElementById('btn');

            oBtn.onclick = function(){

                var num01 = oInput01.value;

                var num02 = oInput02.value;

                var fuhao = oFuhao.value;

                //验证是否为空

                if(num01==''||num02==''){

                    alert('输入框不能为空！');

                    return;

                }

                if(isNaN(num01)||isNaN(num02)){

                    alert('请输入数字！');

                    return;

                }

                switch (fuhao){

                    //这个value是字符串！

                    case "0":

                        alert((parseFloat(num01)*100+parseFloat(num02)*100)/100);

                        break;

                    case '1':

                        alert((parseFloat(num01)*100-parseFloat(num02)*100)/100);

                        break;

                    case "2":

                        alert(((parseFloat(num01)*100)*(parseFloat(num02)*100))/10000);

                        break;

                    case '3':

                        alert(((parseFloat(num01)*100)/(parseFloat(num02)*100)));

                }

            }

        }

    </script>

</head>

<body>

    <h1>计算器</h1>

    <input type="text" name="" id="input01">

    <select id="fuhao">

        <option value="0">+</option>

        <option value="1">-</option>

        <option value="2">*</option>

        <option value="3">/</option>

    </select>

    <input type="text" name="" id="input02">

    <input type="button" name="" value="计算" id="btn">

</body>

</html>