老师帮忙检查下作业，是否可以优化下

来源：4-8 编程练习

技术为王2383098363

2019-08-15 14:51:34

<!DOCTYPE html>
<html>
<head>
    <title> 事件</title>
</head>
<body>
    <input type='text' id='num1' />
    <select id='operate'>
        <option value='+'>+</option>
        <option value="-">-</option>
        <option value="*">*</option>
        <option value="/">/</option>
    </select>
    <input type='text' id='num2' />
    <input type='button' value=' = ' onclick="count()" />
    <input type='text' id='result' />
    <script type="text/javascript">
    function getEleById(idName){
        return document.getElementById(idName);
    }

    function count() {
        var calculator={
        result:getEleById('result'),
        operate:getEleById('operate'),
        num1:getEleById('num1'),
        num2:getEleById('num2')
        } ;
        var operation={
        add:function(num1,num2){return +num1 + +num2},
        subtract:function(num1,num2){return num1-num2},
        multiply:function(num1,num2){return num1*num2},
        divide:function(num1,num2){return num1/num2}
        };

        switch(calculator.operate.value){
            case '+':
                 calculator.result.value=operation.add(calculator.num1.value,calculator.num2.value);
                 break;
            case '-':
                 calculator.result.value=operation.subtract(calculator.num1.value,calculator.num2.value);
                 break;
            case '*':
                 calculator.result.value=operation.multiply(calculator.num1.value,calculator.num2.value);
                 break;
            case '/':
                 calculator.result.value=operation.divide(calculator.num1.value,calculator.num2.value);
                 break;
        }

    } 

    </script>
</body>
</html>

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