将数组中的项目替换为不同集合中的元素

我不确定递归地处理这个问题的正确方法。 假设我有两个数组

array1 = [a, null, c, d, e]

array2 = [1, 2, 3]

我想创建一个以下形式的结果数组

[
   [a, 1, c, d, e],
   [a, 2, c, d, e],
   [a, 3, c, d, e]
]

其中第二个数组的每个元素都填充 n​​ull 的位置。我能够很好地做到这一点，但是如果我有两个 null 情况怎么办？

array1 = [a, null, c, null, e]

array2 = [1, 2, 3]

我如何获得以下内容？

[
   [a, 1, c, 1, e],
   [a, 1, c, 2, e],
   [a, 1, c, 3, e],
   [a, 2, c, 1, e],
   ...
   [a, 3, c, 3, e]
]

JavaScript 代码：

let array1 = ['a', null, 'c', null, 'e']
let array2 = [1, 2, 3]

let output = []
let cursorPosition = 0; // cursorPosition is a pointer for `array2` index
let nullPositions = []

// find nullable positions; in our case here will be 1, 4
for (let i = 0; i < array1.length; i++) {
  if (array1[i] === null) {
    nullPositions.push(i)
  }
}

// find total expected numbers of arrays from given input and create that array
const totalArray = Math.pow(array2.length, nullPositions.length);
for (let i = 0; i < totalArray; i++) {
  output.push([...array1])
}

// replacement logic for the `null` values
for (let i = 0; i < nullPositions.length; i++) {
  cursorPosition = 0;
  // frequency: how often the cursor needs to change (depends on null position)
  let frequency = totalArray / Math.pow(array2.length, i + 1);
  let resetCursorPositionOn = frequency;
  for (let j = 0; j < output.length; j++) {
    if (j < resetCursorPositionOn) {
      output[j][nullPositions[i]] = array2[cursorPosition];
    } else {
      resetCursorPositionOn += frequency;
      cursorPosition++;
      if (cursorPosition === array2.length) {
        cursorPosition = 0;
      }
      output[j][nullPositions[i]] = array2[cursorPosition];
    }
  }
}
console.log(output);

Output:

[
  ["a",1,"c",1,"e"],
  ["a",1,"c",2,"e"],
  ["a",1,"c",3,"e"],
  ["a",2,"c",1,"e"],
  ["a",2,"c",2,"e"],
  ["a",2,"c",3,"e"],
  ["a",3,"c",1,"e"],
  ["a",3,"c",2,"e"],
  ["a",3,"c",3,"e"]
]

它可以任意组合使用。