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javascript - 如何使用下拉框和预定值计算总计

问题描述

我试图通过从这些下拉框中获取值并通过具有预设值的函数运行它们来获得计算的总数，但它不返回任何内容。警告框也没有弹出，谁能告诉我这里到底出了什么问题？

这是我的代码片段：

<!DOCTYPE html>
<html>
<head>

<script>
    function calcTotal(){
        var numAdult = parseInt(document.getElementById('adultStandard').value);
        var numConcession = parseInt(document.getElementById('concessionStandard').value);
        var numChild = parseInt(document.getElementById('childStandard').value);

        var adultStandard = 10.10;
        var concessionStandard = 11.50;
        var childStandard = 12.70;

        var saleTotal = (adultStandard * numAdult) + (concessionStandard * numConcession) + (childStandard * numChild);

        document.getElementById('totalCost').innerHTML = "test";

        return true;
        alert("Total is: " saleTotal);
    }

</script>
</head>
<body>
<form action onchange='return calcTotal()' method='post'>
Adult: 
<select id='adultStandard' name='adultStandard'>
    <script>
        var maxqty = 10;
        for ( var i=0; i<=maxqty; i++ )
        document.write('<option value="'+i+'">'+i+'</option>');
    </script>
</select>
<br>
Concession: 
<select id='concessionStandard' name='concessionStandard'>
    <script>
        var maxqty = 10;
        for ( var i=0; i<=maxqty; i++ )
        document.write('<option value="'+i+'">'+i+'</option>');
    </script>
</select>
<br>
Child: 
<select id='childStandard' name='childStandard'>
    <script>
        var maxqty = 10;
        for ( var i=0; i<=maxqty; i++ )
        document.write('<option value="'+i+'">'+i+'</option>');
    </script>
</select>
<br>
<label>
Total: $<input id='totalCost' readonly='readonly' value='0'>
</label>
</form>
</body>
</html>

标签： javascriptphphtml

解决方案

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