数组数学逻辑 JavaScript答案

【问题标题】：Arrays Math Logic JavaScript数组数学逻辑 JavaScript
【发布时间】：2015-12-10 00:03:44
【问题描述】：

我似乎无法列出数组中偶数的数量，当我将数组整数乘以乘数时也无法得到结果。想了很久，想不出来了。提前致谢！

<!DOCTYPE HTML>
<html>

<head>
<meta charset="utf-8">
<title>EvensMultiply</title>
<script type="text/javascript">
    /*Write a defining table and a function named countEvens that counts and returns the number of even integers in an array. The function must have this header: function countEvens(list)*/

    // This function will call and test countEvens() and multiply(list, multiplier).
    function testFunctions() {
        var list = [17, 8, 9, 5, 20];
        var multiplier = 3;
        var result1 = 0;
        var result2 = 0;
        var result3 = 0;
        result1 = countEvens(list);
        //result2 = multiply(list, multiplier);
        result3 = "These are the even numbers of the array list: " + result1 + "<br>" + "This is the array list multiplied by 3: " + result2;
        document.getElementById("outputDiv").innerHTML = result3;
    }
    // This function will find the even intergers in the array.
    function countEvens(list) {
        var evens = [];
        for (var i = 0; i < list.length; ++i) {
            if ((list[i] % 2) === 0) {
                evens.push(list[i]);
                return evens;
            }
        }

    }
    /*Write a defining table and a function to multiply each element in an array by some value. The function must have this header: function multiply(list, multiplier)*/

    // This function will multiply the array list by a multiplier.
    function multiply(list, multiplier) {
        var products;
            products=list.map(function(list){return list * multiplier;});
        return products;
    }
 </script>
 </head>
 <h1>Find evens and multiply by multiplier.</h1>
 <h2>Array list [17, 8, 9, 5, 20]</h2>
 <h3>Click the Compute button to test.</h3>
 <button type="button" onclick="testFunctions()">Compute</button>
 <div id="outputDiv"></div>

 </html>

【问题讨论】：

标签： javascript arrays math logic

【解决方案1】：

循环完成后需要返回：

// This function will find the even intergers in the array.
function countEvens(list) {
    var evens = [];
    for (var i = 0; i < list.length; ++i) {
        if ((list[i] % 2) === 0) {
            evens.push(list[i]);
        }
    }
    return evens;
}

【讨论】：

【解决方案2】：

嗨，这里出现了一个小的编码疏忽，用于计算偶数。您的“返回偶数”只是在将偶数推入“偶数数组”之后，所以基本上您过早地跳出了功能。请把下面的函数当作修改函数，（注意return语句）

function countEvens(list) {
        var evens = [];
        for (var i = 0; i < list.length; ++i) {
            if ((list[i] % 2) === 0) {
                evens.push(list[i]);
            }
        }
        return evens;

    }

【讨论】：

取消注释 result2 乘法语句以使乘法工作。
谢谢！我现在得到另一个偶数。但是，乘法函数我仍然得到 0。
您是否取消了“result2 = multiply(list, multiplier);”行的注释
哇！我觉得我好笨。我已经在这里呆了好几个小时了，我再也看不清楚了。谢谢！