Question

我正在研究FCC中间算法“可选参数”。这是有关需要发生的情况的说明：

中间算法脚本：参数可选

创建一个将两个参数加在一起的函数。如果仅提供一个参数，则返回一个期望一个参数并返回总和的函数。
例如，addTogether（2，3）应该返回5，而addTogether（2）应该返回一个函数。
使用单个参数调用此返回的函数将返回总和： var sumTwoAnd = addTogether（2）; sumTwoAnd（3）返回5。
如果任一自变量都不是有效数字，则返回undefined。

我写了代码来完成上面解释的所有事情，但是一个要求是参数必须全部是数字，否则返回undefined（上面的＃4）。您会看到我写了一个三元运算符（我的代码的第5行）numbersOnly变量，我认为它可以处理此变量，但这只是在控制台中返回[Function]。

function addTogether() {
    // Convert args to an array
    let args = [...arguments];
    // Only accept numbers or return undefined and stop the program
    const numbersOnly = value => typeof(value) === 'number'? value : undefined;
    // test args for numbersOnly and return only the first two arguments regardless of the length of args
    let numbers = args.filter(numbersOnly).slice(0, 2);

    // // It has to add two numbers passed as parameters and return the sum.
    if (numbers.length > 1) {
        return numbers[0] + numbers[1];
    }
    // If it has only one argument then it has to return a function that uses that number and expects another one, to then add it.
    else if (numbers.length === 1) {
        let firstParam = numbers[0];
        return function(secondParam) {
            if (typeof secondParam !== 'number' || typeof firstParam !== 'number') {
                return undefined;
            }
            return secondParam + firstParam;
        }
    }
}

我正在通过所有测试，但＃4除外，该测试应返回未定义。我不太明白为什么5通过并返回undefined但4失败。我在这里想念什么？谢谢！

1. addTogether(2, 3) should return 5.
2. addTogether(2)(3) should return 5.
3. addTogether("https://www.youtube.com/watch?v=dQw4w9WgXcQ") should return undefined.
4. addTogether(2, "3") should return undefined.
5. addTogether(2)([3]) should return undefined.

Answer 1

这是因为您必须检查过滤器的输入参数和输出参数。尝试添加以下代码段：

let numbers = args.filter(numbersOnly).slice(0, 2);
if (args.length > numbers.length) {
  return undefined;
}

function addTogether() {
    // Convert args to an array
    let args = [...arguments];
    // Only accept numbers or return undefined and stop the program
    const numbersOnly = value => typeof(value) === 'number'? value : undefined;
    // test args for numbersOnly and return only the first two arguments regardless of the length of args
    let numbers = args.filter(numbersOnly).slice(0, 2);
    if (args.length > numbers.length) {
      return undefined;
    }

    // // It has to add two numbers passed as parameters and return the sum.
    if (numbers.length > 1) {
        return numbers[0] + numbers[1];
    }
    // If it has only one argument then it has to return a function that uses that number and expects another one, to then add it.
    else if (numbers.length === 1) {
        let firstParam = numbers[0];
        return function(secondParam) {
            if (typeof secondParam !== 'number' || typeof firstParam !== 'number') {
                return undefined;
            }
            return secondParam + firstParam;
        }
    }
  }
  console.log('4. addTogether', addTogether(4, "4"));

Answer 2

由于过滤参数时，只有'3'被过滤掉，因此剩余数组的长度为1。

const args = [2, '3'];
const numbers = args.filter((n) => typeof n === 'number');
console.log('numbers:', numbers);
console.log('numbers.length === 1:', numbers.length === 1);

三元运算符未返回未定义

2 个答案: