javascript - 数组不推送预期的元素

Question

我正在学习 JavaScript 并遇到了这个问题。基本上我必须检查无效的信用卡号码

// All valid credit card numbers
const valid1 = [4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8]
const valid2 = [5, 5, 3, 5, 7, 6, 6, 7, 6, 8, 7, 5, 1, 4, 3, 9]
const valid3 = [3, 7, 1, 6, 1, 2, 0, 1, 9, 9, 8, 5, 2, 3, 6]
const valid4 = [6, 0, 1, 1, 1, 4, 4, 3, 4, 0, 6, 8, 2, 9, 0, 5]
const valid5 = [4, 5, 3, 9, 4, 0, 4, 9, 6, 7, 8, 6, 9, 6, 6, 6]

// All invalid credit card numbers
const invalid1 = [4, 5, 3, 2, 7, 7, 8, 7, 7, 1, 0, 9, 1, 7, 9, 5]
const invalid2 = [5, 7, 9, 5, 5, 9, 3, 3, 9, 2, 1, 3, 4, 6, 4, 3]
const invalid3 = [3, 7, 5, 7, 9, 6, 0, 8, 4, 4, 5, 9, 9, 1, 4]
const invalid4 = [6, 0, 1, 1, 1, 2, 7, 9, 6, 1, 7, 7, 7, 9, 3, 5]
const invalid5 = [5, 3, 8, 2, 0, 1, 9, 7, 7, 2, 8, 8, 3, 8, 5, 4]

// Can be either valid or invalid
const mystery1 = [3, 4, 4, 8, 0, 1, 9, 6, 8, 3, 0, 5, 4, 1, 4]
const mystery2 = [5, 4, 6, 6, 1, 0, 0, 8, 6, 1, 6, 2, 0, 2, 3, 9]
const mystery3 = [6, 0, 1, 1, 3, 7, 7, 0, 2, 0, 9, 6, 2, 6, 5, 6, 2, 0, 3]
const mystery4 = [4, 9, 2, 9, 8, 7, 7, 1, 6, 9, 2, 1, 7, 0, 9, 3]
const mystery5 = [4, 9, 1, 3, 5, 4, 0, 4, 6, 3, 0, 7, 2, 5, 2, 3]

// An array of all the arrays above
const batch = [valid1, valid2, valid3, valid4, valid5, invalid1, invalid2, invalid3, invalid4, invalid5, mystery1, mystery2, mystery3, mystery4, mystery5]

通过这个算法（Luhn 算法）访问信用卡的有效性：

function validateCred(card_number){
let sum = card_number[card_number.length-1];
let flag = 1;
for (i = card_number.length-2; i >= 0; i--){
    if (flag % 2 !== 0){
        card_number[i] *= 2;
        if (card_number[i] > 9){
            card_number[i] -= 9;
        }
    }
    sum += card_number[i];
    flag++;
}

if (sum % 10 === 0){
    return true;
} else {
    return false;
}
}

我必须创建一个包含所有无效卡的数组：

function findInvalidCards(numbers){
    let invalid_array = [];
    for (i = 0; i < numbers.length; i++){
        if (!validateCred(numbers[i])){
            invalid_array.push(numbers[i]);
        }
    }
    return invalid_array;
}

当我调用该findInValidCards函数时，它会引发heap out of memory错误，我尝试遵循此链接中的解决方案并将使用内存提高到 8gb，但问题仍然存在。经过调试，我发现这行invalid_array.push(numbers[i])实际上是在数组中附加了一个undefined变量，而不是我想要的元素。什么可能导致这个问题？

标签： javascript

Answer 1

正如 Nina 在评论中所说，您应该在每次编写 for 循环时进行定义i，let否则您将遇到不可预知的行为

但是，您的validateCred函数中也有一个问题，您在检查原始数组时对其进行了变异 - 您可以简单地克隆输入数组let clone = card_number.slice(0);，然后参考clone您的检查

findInvalidCards此外，您可以使用进行简化.filter()，例如：

function findInvalidCards(numbers) {
  return numbers.filter(x => !validateCred(x));
}

// All valid credit card numbers
const valid1 = [4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8];
const valid2 = [5, 5, 3, 5, 7, 6, 6, 7, 6, 8, 7, 5, 1, 4, 3, 9];
const valid3 = [3, 7, 1, 6, 1, 2, 0, 1, 9, 9, 8, 5, 2, 3, 6];
const valid4 = [6, 0, 1, 1, 1, 4, 4, 3, 4, 0, 6, 8, 2, 9, 0, 5];
const valid5 = [4, 5, 3, 9, 4, 0, 4, 9, 6, 7, 8, 6, 9, 6, 6, 6];

// All invalid credit card numbers
const invalid1 = [4, 5, 3, 2, 7, 7, 8, 7, 7, 1, 0, 9, 1, 7, 9, 5];
const invalid2 = [5, 7, 9, 5, 5, 9, 3, 3, 9, 2, 1, 3, 4, 6, 4, 3];
const invalid3 = [3, 7, 5, 7, 9, 6, 0, 8, 4, 4, 5, 9, 9, 1, 4];
const invalid4 = [6, 0, 1, 1, 1, 2, 7, 9, 6, 1, 7, 7, 7, 9, 3, 5];
const invalid5 = [5, 3, 8, 2, 0, 1, 9, 7, 7, 2, 8, 8, 3, 8, 5, 4];

// Can be either valid or invalid
const mystery1 = [3, 4, 4, 8, 0, 1, 9, 6, 8, 3, 0, 5, 4, 1, 4];
const mystery2 = [5, 4, 6, 6, 1, 0, 0, 8, 6, 1, 6, 2, 0, 2, 3, 9];
const mystery3 = [6, 0, 1, 1, 3, 7, 7, 0, 2, 0, 9, 6, 2, 6, 5, 6, 2, 0, 3];
const mystery4 = [4, 9, 2, 9, 8, 7, 7, 1, 6, 9, 2, 1, 7, 0, 9, 3];
const mystery5 = [4, 9, 1, 3, 5, 4, 0, 4, 6, 3, 0, 7, 2, 5, 2, 3];

// An array of all the arrays above
const batch = [valid1, valid2, valid3, valid4, valid5, invalid1, invalid2, invalid3, invalid4, invalid5, mystery1, mystery2, mystery3, mystery4, mystery5];

function validateCred(card_number) {
  let clone = card_number.slice(0);

  let sum = clone[clone.length - 1];
  let flag = 1;

  for (i = clone.length - 2; i >= 0; i--) {
    if (flag % 2 !== 0) {
      clone[i] *= 2;
      if (clone[i] > 9) {
        clone[i] -= 9;
      }
    }

    sum += clone[i];
    flag++;
  }

  if (sum % 10 === 0) {
    return true;
  } else {
    return false;
  }
};

// And I have to create an array with all the invalid cards:
function findInvalidCards(numbers) {
  let invalid_array = [];
  for (let i = 0; i < numbers.length; i++) {
    if (!validateCred(numbers[i])) {
      invalid_array.push(numbers[i]);
    }
  }
  return invalid_array;
}

let invalidCardArray = findInvalidCards(batch);

// Prettier console.log()
invalidCardArray.forEach(x => console.log(validateCred(x) + ':', ...x));