JavaScript 输出 returns 未定义

Question

我最近开始 JavaScript 并一直在研究一个简单的税收计算器，我遇到的唯一问题是输出 returns undefined 而不是预期值。比如我输入320000，所得税应该是14000，但是return没有定义。我尝试将 calculation 设置为 0 但它没有解决问题。是什么让我的函数不是 return 预期值？我查看了我的大学提供的示例程序，这些程序在条件语句中使用变量并且它们工作正常，但我的不是。

function calculateTax()
{
    var taxableIncome, calculation;
    taxableIncome = document.getElementById("t").value * 1;

    if (taxableIncome > 250000) {
        calculation = 0;
    }
    else if (taxableIncome > 250000 && taxableIncome < 40000) {
        calculation = (taxableIncome - 250000) * 0.20; 
    }
    else if (taxableIncome > 400000 && taxableIncome < 800000) {
        calculation = ((taxableIncome - 400000) * 0.25) + 30000;
    }
    else if (taxableIncome > 800000 && taxableIncome < 2000000) {
        calculation = ((taxableIncome - 800000) * 0.30) + 130000;
    }
    else if (taxableIncome > 2000000 && taxableIncome < 8000000) {
        calculation = ((taxableIncome - 2000000) * 0.32);
    }
    else if (taxableIncome > 8000000) {
        calculation = ((taxableIncome - 8000000) * 0.35) + 2410000;
    }

    document.getElementById("inputTax").innerHTML = "The taxable income is:" +taxableIncome;
    document.getElementById("incomeTax").innerHTML = "The income tax is:" +calculation;
}

<h1>Income Tax Calculator</h1>

<p>
<label for = "t">Taxable Income</label> 
<input type = "number" id="t" name="t">
<button onclick = "calculateTax()"> Calculate Tax </button>
</p>

<h2 id="inputTax"></h2>
<h2 id="incomeTax"></h2>

Answer 1

对于值 320000，对于 taxableIncome > 250000 和 returns 0，条件始终为 true。此外，值 40000（用于第二个条件）和 400000（用于第三个条件）之间存在不匹配。

您应该将以下前两个条件更改为：

if (taxableIncome < 250000) {

else if (taxableIncome > 250000 && taxableIncome < 400000) {

请注意：您不需要检查最终条件（taxableIncome > 8000000），只有 else 可以。

演示：

function calculateTax()
{
    var taxableIncome, calculation;
    taxableIncome = document.getElementById("t").value * 1;

    if (taxableIncome < 250000) {
        calculation = 0;
    }
    else if (taxableIncome > 250000 && taxableIncome < 400000) {
        calculation = (taxableIncome - 250000) * 0.20; 
    }
    else if (taxableIncome > 400000 && taxableIncome < 800000) {
        calculation = ((taxableIncome - 400000) * 0.25) + 30000;
    }
    else if (taxableIncome > 800000 && taxableIncome < 2000000) {
        calculation = ((taxableIncome - 800000) * 0.30) + 130000;
    }
    else if (taxableIncome > 2000000 && taxableIncome < 8000000) {
        calculation = ((taxableIncome - 2000000) * 0.32);
    }
    else{
        calculation = ((taxableIncome - 8000000) * 0.35) + 2410000;
    }

    document.getElementById("inputTax").innerHTML = "The taxable income is:" +taxableIncome;
    document.getElementById("incomeTax").innerHTML = "The income tax is:" +calculation;
}

<h1>Income Tax Calculator</h1>

<p>
<label for = "t">Taxable Income</label> 
<input type = "number" id="t" name="t">
<button onclick = "calculateTax()"> Calculate Tax </button>
</p>

<h2 id="inputTax"></h2>
<h2 id="incomeTax"></h2>

JavaScript 输出 returns 未定义

JavaScript output returns undefined

javascript

function

undefined

conditional-statements