Javascript计算产生意想不到的结果

Javascript Calculations Producing Unexpected Results

本文关键字：结果 意想不到 计算 Javascript      更新时间：2023-09-26
<head>
    <title>Javascript Test</title>
</head>
<body>
<script>
        function calc_form() {
            discPerc = document.forms["calc"].elements["disc_perc"].value;
            totDays = document.forms["calc"].elements["tot_days"].value;
            discPer = document.forms["calc"].elements["disc_per"].value;
            discDays = document.forms["calc"].elements["disc_days"].value;
            discCalc = Math.round([(discPerc/100)/((100-discPerc)/100)]*(totDays/(discPer-discDays)));
            document.forms["calc"].elements["result"].value = discCalc*100 + "%";
            document.getElementById("result1").innerHTML = discCalc*100 + "%";
            //return Math.round(discCalc);
        }
    </script>
<form name = "calc">
    Discount Percentage:
    <br>
    <input type = "text" name="disc_perc">
    <br>
    Enter Total Days in a year:
    <br>
    <input type="text" name="tot_days">
    <br>
    Enter Discount Days:
    <br>
    <input type="text" name="disc_days">
    <br>
    Enter Discount Period
    <br>
    <input type="text" name="disc_per">
    <input type="button" value="Calculate" onclick = "calc_form()">
    <br>   <br>
    Cost of forgoing discount:
    <br>
    <input type="text" id="result">
</form>
<p id="result1"></p>
</body>

上面的代码正在生成意外的结果。当然，其中有一个错误，但我无法理解。当我在 Math.round 函数中封装 discCalc 变量时，输出与我不这样做时完全不同。

请有人解释这种差异。

谢谢。

我只是通过使用变量.toFixed（2）而不是使用Math.round（）函数来解决这个问题。所以代码是：

<script>
        function calc_form() {
            discPerc = document.forms["calc"].elements["disc_perc"].value;
            totDays = document.forms["calc"].elements["tot_days"].value;
            discPer = document.forms["calc"].elements["disc_per"].value;
            discDays = document.forms["calc"].elements["disc_days"].value;
            //discCalc = Math.round([(discPerc/100)/((100-discPerc)/100)]*(totDays/(discPer-discDays)));
            discCalc = [(discPerc)/((100-discPerc))]*(totDays/(discPer-discDays));
            discCalc_2 = discCalc*100;
            document.forms["calc"].elements["result"].value = discCalc_2.toFixed(2) + "%";
            document.getElementById("result1").innerHTML = discCalc_2.toFixed(2) + "%";
            //return Math.round(discCalc);
        }
    </script>
<form name = "calc">
    Discount Percentage:
    <br>
    <input type = "text" name="disc_perc">
    <br>
    Enter Total Days in a year:
    <br>
    <input type="text" name="tot_days">
    <br>
    Enter Discount Days:
    <br>
    <input type="text" name="disc_days">
    <br>
    Enter Discount Period
    <br>
    <input type="text" name="disc_per">
    <input type="button" value="Calculate" onclick = "calc_form()">
    <br>   <br>
    Cost of forgoing discount:
    <br>
    <input type="text" id="result">
</form>
<p id="result1"></p>
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