JavaScript简易计算器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JS计算器</title>
    <link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css">
</head>
<body style="margin:50px">
    <div class="form-group">
        <div class="col-sm-3">
            <input type="text" id="sum1" class="form-control" placeholder="请输入第一个数">
        </div>
        <div class="col-sm-2">
            <select id="sign" class="form-control">
            <option>加</option>
            <option>减</option>
            <option>乘</option>
            <option>除</option>
            <option>取余</option>
        </select>
        </div>
        <div class="col-sm-3">
            <input type="text" id="sum2" placeholder="请输入第二个数" class="form-control">
        </div>
        <div class="col-sm-1">
            <button id="equal" class="btn btn-info" style="width:100%;" onclick="equals()">=</button>
        </div>
        <div class="col-sm-3">
            <label id="count"class="form-control"></label>
        </div>
    </div>

    <script type="text/javascript">
        var sum1;
        var sum2;
        var sign;
        var fruit;
        function equals(){
            sum1 = parseInt(document.getElementById("sum1").value);
            sum2 = parseInt(document.getElementById("sum2").value);
            if (isNaN(sum1) || isNaN(sum2)) {
                document.getElementById("count").innerHTML = "您输入的不是数字，请重新输入!";
            }else{
                sign = document.getElementById("sign").value;

                switch(sign){
                    case '加':
                        fruit = sum1 + sum2;
                        break;
                    case '减':
                        fruit = sum1 - sum2;
                        break;
                    case '乘':
                        fruit = sum1 * sum2;
                        break;
                    case '除':
                        if (sum2 == 0) {
                            fruit = "被除数不能为0，请重新输入!";
                            break;
                        }else{
                            fruit = sum1 / sum2;
                            break;
                        }
                    case '取余':
                        fruit = sum1 % sum2;
                        break;
                }
                document.getElementById("count").innerHTML = fruit;
                };
            }
    </script>
</body>
</html>
JavaScript简易计算器

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