Question

我有一个对象，我想循环并返回数组中每个键的累积长度。以下是对象和理想的输出：

const books = {
    "book_1": ["image-1", "image-2", "image-3"], // 3
    "book_2": ["image-1"], // 1
    "book_3": ["image-1", "image-2"] // 2
}

// Ideal Output
[3, 4, 6]

我知道不可能遍历对象，但是我先使用Object.key()然后使用.reduce()来获取每个键的长度，但我只是想不出如何分割它们一起。任何帮助将不胜感激

const books = {
    "book_1": ["image-1", "image-2", "image-3"], // 3
    "book_2": ["image-1"], // 1
    "book_3": ["image-1", "image-2"] // 2
}

console.log(Object.keys(books).reduce(function (accumulator, currentValue, index) {
  console.log(books[Object.keys(books)[index]].length)
  
  return currentValue;
}, []))

Answer 1

const books = {
    "book_1": ["image-1", "image-2", "image-3"], // 3
    "book_2": ["image-1"], // 1
    "book_3": ["image-1", "image-2"] // 2
}

console.log(Object.entries(books).reduce((acc, [key, array]) => {
  acc.push((acc.slice(-1)[0] || 0) + array.length);
  return acc;
}, []))

但是...由于不能保证按键顺序，您可能会得到

const books = {
    "book_2": ["image-1"], // 1
    "book_1": ["image-1", "image-2", "image-3"], // 3
    "book_3": ["image-1", "image-2"] // 2
}

console.log(Object.entries(books).reduce((acc, [key, array]) => {
  acc.push((acc.slice(-1)[0] || 0) + array.length);
  return acc;
}, []))

您想要我正在猜测的特定顺序-因此，对键进行排序

const books = {
    "book_2": ["image-1"], // 1
    "book_1": ["image-1", "image-2", "image-3"], // 3
    "book_3": ["image-1", "image-2"] // 2
}

console.log(Object.entries(books).sort(([a], [b]) => a.localeCompare(b)).reduce((acc, [key, array]) => {
  acc.push((acc.slice(-1)[0] || 0) + array.length);
  return acc;
}, []))

Answer 2

虽然还是可以遍历对象。

const books = {
"book_1": ["image-1", "image-2", "image-3"], // 3
"book_2": ["image-1"], // 1
"book_3": ["image-1", "image-2"] // 2
}

let sum = 0;
let arr = [];

for(let i in books){
  sum += books[i].length;
  arr.push(sum);
}

console.log(arr);//[3,4,6]

循环遍历对象并累积返回数组中每个键的长度

2 个答案: