返回一个对象值作为另一个对象值出现的次数的数字

问题描述

accounts 数组中的 account 对象示例：

const accounts = [
  {
    id: "5f446f2ecfaf0310387c9603",picture: "https://api.adorable.io/avatars/75/[e-mail]",age: 25,name: {
      first: "Esther",last: "Tucker",},company: "ZILLACON",email: "[e-mail]",registered: "Thursday,May 28,2015 2:51 PM",

books 数组中的 book 对象示例：

const books = [
  {
    id: "5f447132d487bd81da01e25e",title: "sit eiusmod occaecat eu magna",genre: "Science",authorId: 8,borrows: [
      {
        id: "5f446f2e2cfa3e1d234679b9",returned: false,{
        id: "5f446f2ed3609b719568a415",returned: true,{
        id: "5f446f2e1c71888e2233621e",{
        id: "5f446f2e6059326d9feb9a68",{
        id: "5f446f2ede05a0b1e3394d8b",{
        id: "5f446f2e4081699cdc6a2735",{
        id: "5f446f2e3900dfec59489477",{
        id: "5f446f2e409f8883af2955dd",{
        id: "5f446f2eae901a82e0259947",{
        id: "5f446f2ef2ab5f5a9f60c4f2",{
        id: "5f446f2ea6b68cf6f85f6e28",{
        id: "5f446f2eed18105706d6ca19",{
        id: "5f446f2e91c2af00cb74e82b",{
        id: "5f446f2e5aa2bb5545a0f8a6",{
        id: "5f446f2ea508b6a99c3e42c6",{
        id: "5f446f2e50cc2da9cd80efdb",{
        id: "5f446f2e0b3e2ff72fc503e7",{
        id: "5f446f2ef795e593cd3cd19d",{
        id: "5f446f2e2f35653fa80bf490",{
        id: "5f446f2e7b9cd304fed3a8bc",{
        id: "5f446f2ed9aac23c0340aab2",],

我需要我的函数返回一个数字，表示帐户 ID 在任何书籍的 borrow 数组中出现的次数。

这是我所拥有的：

function getTotalNumberOfBorrows(account,books) {
  const accId = account.id;
  let idBorrowed = books.filter((book) => accId === book.borrows.id);
  return idBorrowed.length;
}

当我应该在测试中得到 2 时，我得到了 0。请注意，我刚刚完成了高级函数的学习，预计会在需要时使用查找、过滤、映射、缩减和解构对象。感谢您提供任何帮助/建议。

解决方法

borrows 是一个数组，您需要对其进行迭代以获取每次借用的 id 属性。

function getTotalNumberOfBorrows(account,books) {
  const accId = account.id;
  let total = 0;
  books.forEach(book => book.borrows.forEach(borrow => accId === borrow.id && total++));
  return total;
}

,

如果您需要使用“高级”功能的另一种可能方法

function getTotalNumberOfBorrows(account,books) {
  const { id: accId } = account;

  return books.reduce((accumulator,book) => {
    return (
      accumulator +
      book.borrows
        .filter(borrow => borrow.id === accId)
        .reduce((accumulatorBorrows,borrow) => accumulatorBorrows + 1,0)
    );
  },0);
}

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