returns 对象命名的函数

Question

const parks = [
    {
      id: 1,
      name: "Acadia",
      areaInSquareKm: 198.6,
      location: { state: "Maine" },
    },
    {
      id: 2,
      name: "Canyonlands",
      areaInSquareKm: 1366.2,
      location: { state: "Utah" },
    },
    {
      id: 3,
      name: "Crater Lake",
      areaInSquareKm: 741.5,
      location: { state: "Oregon" },
    },
    {
      id: 4,
      name: "Lake Clark",
      areaInSquareKm: 10602,
      location: { state: "Alaska" },
    },
    {
      id: 5,
      name: "Kenai Fjords",
      areaInSquareKm: 2710,
      location: { state: "Alaska" },
    },
    {
      id: 6,
      name: "Zion",
      areaInSquareKm: 595.9,
      location: { state: "Utah" },
    },
  ];

  const users = {
    "karah.branch3": {
      visited: [1],
      wishlist: [4, 6],
    },
    "dwayne.m55": {
      visited: [2, 5, 1],
      wishlist: [],
    },
    thiagostrong1: {
      visited: [5],
      wishlist: [6, 3, 2],
    },
    "don.kim1990": {
      visited: [2, 6],
      wishlist: [1],
    },
  };

我需要创建一个函数来执行此操作：此函数 returns 所有访问过给定用户愿望清单上任何公园的用户名。

getUsersForUserWishlist(users, "karah.branch3"); //> ["dwayne.m55"]
getUsersForUserWishlist(users, "dwayne.m55"); //> []

这是我目前所拥有的，但它不起作用：

function getUsersForUserWishlist(users, userId) {
  let wish = userId.wishlist;
  return users[userId].visited.map((visited) => wish.includes(visited));
}

请记住：我刚刚完成了课程的一部分，其中涵盖了高级功能（查找、过滤、映射、某些、每个、forEach），我应该使用它们来解决问题。

Answer 1

让我们回顾一下您的尝试：

let wish = userId.wishlist;

这里，userId是一个字符串。一个字符串没有属性wishlist。您需要获取该 ID 对应的用户对象：users[userId].wishlist。就像你在第二行所做的那样：

users[userId].visited.map((visited) => wish.includes(visited));

但是，map is not the best method for what you want to achieve. You want to filter the user names to keep only the ones that pass a condition. Which is that some parks in the wishlist are included 在该用户的已访问公园列表中：

const users= {
  "karah.branch3": { visited: [1], wishlist: [4,6] },
  "dwayne.m55": { visited: [2,5,1], wishlist: [] },
  "thiagostrong1": { visited: [5], wishlist: [6,3,2] },
  "don.kim1990": { visited: [2,6], wishlist: [1] }
};

function getUsersForUserWishlist(users, userId) {
  const wishlist = users[userId].wishlist;
  // Get all user names
  return Object.keys(users)
    // Filter them
    .filter(
      // If the wishlist has some elements which that user has visited
      name => wishlist.some(park => users[name].visited.includes(park))
    );
}

console.log(getUsersForUserWishlist(users, "karah.branch3")); //> ["don.kim1990"]
console.log(getUsersForUserWishlist(users, "dwayne.m55")); //> []

returns 对象命名的函数

function that returns object names

javascript

arrays

function

higher-order-functions

javascript-objects