使用给定的键数组获取对象字段

Question

鉴于这一目标：

const userData = {
  avatar: undefined,
  name: "Raul",
  username: "raulito",
  celebrity: true
}

我需要实现一个方法，该方法接收一个键列表(即"avatar“、"name”、"username")并获取userData对象的相应值，而忽略了未定义的值。

我如何使用现代的javascript语法来做到这一点？

function denormalizeUserData(userData, ...fields) {
  const denormalized = {};

  // For each key (field), get its value from userData, ignoring if undefined
  
  return denormalized;
}

所以，如果我做了：

 denormalizeUserData(userData, "avatar", "name");

方法必须返回我：

{
  name: "Raul,
}

忽略化身，因为它是没有定义的。

这是我的尝试。我需要现代语法。

​

const userData = {
  avatar: undefined,
  name: "Raul",
  username: "raulito",
  celebrity: true
}

function denormalizeUserData(userData, ...fields) {
  const denormalized = {};

  fields.forEach((key) => {
    const value = userData[key];

    if(typeof value !== "undefined") {
      denormalized[key] = value;
    } 
  })

  return denormalized;
}

console.log(denormalizeUserData(userData, "celebrity", "name", "avatar"))

​

Answer 1

function denormalizeUserData(userData, ...fields) {
  const denormalized = {};

  for (const field of fields) {
    if (userData[field] !== undefined) denormalized[field] = userData[field];
  }
  
  return denormalized;
}

编辑:如果有人说，只有代码的答案是废话之类的

这很简单，足以成为一个简单的代码块。

Answer 2

您可以使用Object.entries获取对象属性/值对，然后使用Array.filter筛选出其属性名不包括在fields中且其值为undefined的对，然后使用Object.fromEntries将其转换回对象。

​

const userData = {
  avatar: undefined,
  name: "Raul",
  username: "raulito",
  celebrity: true
}

function denormalizeUserData(userData, ...fields) {
  return Object.fromEntries(Object.entries(userData).filter(e => fields.includes(e[0]) && e[1] != undefined))
}

console.log(denormalizeUserData(userData, "avatar", "name"))

​

Answer 3

如果有值，则获取Object.entries并构建一个新对象，如果args数组includes键。

​

const userData = {
  avatar: undefined,
  name: "Raul",
  username: "raulito",
  celebrity: true
};

function denormalizeUserData(obj, ...args) {
  const out = {};
  for (let [key, value] of Object.entries(obj)) {
    if (value && args.includes(key)) {
      out[key] = value;
    };
  }
  return out;
}

console.log(denormalizeUserData(userData));
console.log(denormalizeUserData(userData, 'avatar', 'name'));
console.log(denormalizeUserData(userData, 'avatar', 'name', 'celebrity'));

​