使用高阶函数，return 一个对象值，如果另一个值是 true (JavaScript)

Question

我有一个对象：

const animals = [
    {name: 'Fluffy', species: 'cat'},
    {name: 'Crinkle', species: 'rabbit'},
    {name: 'Wally', species: 'dog'},
    {name: 'Roo', species: 'dog'},
    {name: 'Felix', species: 'cat'},
]

我想使用高阶函数，例如 filter() 方法来获取动物对象数组，return 一个只包含所有狗的名字的数组，即 ["Wally", "Roo"]。我现在的代码 return 是一个包含整个对象的数组，里面有狗。见下文：

const dogArray = animals.filter(function(animal) {
  return animal.species === 'dog';
 })

return dogArray;

// returns
// [{name: "Wally", species: "dog"}, 
// { name: "Roo", species: "dog"}]

Answer 1

只需将过滤后数组的元素映射到它们的名称属性:

const animals = [
  {name: 'Fluffy', species: 'cat'},
  {name: 'Crinkle', species: 'rabbit'},
  {name: 'Wally', species: 'dog'},
  {name: 'Roo', species: 'dog'},
  {name: 'Felix', species: 'cat'},
]

const dogArray = animals.filter(animal => animal.species === 'dog');

console.log(dogArray.map(dog => dog.name));

或者将两者合二为一 reduce:

const animals = [
  {name: 'Fluffy', species: 'cat'},
  {name: 'Crinkle', species: 'rabbit'},
  {name: 'Wally', species: 'dog'},
  {name: 'Roo', species: 'dog'},
  {name: 'Felix', species: 'cat'},
]

let dogArray = animals.reduce((dogs, animal) => {
  if (animal.species === "dog") dogs.push(animal.name);
  return dogs;
}, []);

console.log(dogArray)

Answer 2

创建一个空数组，使用 for 循环遍历现有 dogArray，将名称推入新数组，然后 return 新数组。

const dogArray = animals.filter(function(animal) {
  return animal.species === 'dog';
 })

let dogNames = [];

for (let i in dogArray) {
  dogNames.push(dogArray[i].name);
}

return dogNames;

Answer 3

const animals = [
{name: 'Fluffy', species: 'cat'},
{name: 'Crinkle', species: 'rabbit'},
{name: 'Wally', species: 'dog'},
{name: 'Roo', species: 'dog'},
{name: 'Felix', species: 'cat'},
]

var result = animals.filter(val=>val.species=="dog").map(({name})=>name);

console.log(result);

Answer 4

您可以将属性映射为 destructuring。

const
    animals = [{ name: 'Fluffy', species: 'cat' }, { name: 'Crinkle', species: 'rabbit' }, { name: 'Wally', species: 'dog' }, { name: 'Roo', species: 'dog' }, { name: 'Felix', species: 'cat' }]
    dogArray = animals
        .filter(({ species }) => species === 'dog')
        .map(({ name }) => name);

console.log(dogArray);

Answer 5

您可以使用 .filter() 后跟 .map():

const animals = [
  {name: 'Fluffy', species: 'cat'},
  {name: 'Crinkle', species: 'rabbit'},
  {name: 'Wally', species: 'dog'},
  {name: 'Roo', species: 'dog'},
  {name: 'Felix', species: 'cat'},
];

const dogNames = animals
  .filter(animal => animal.species === 'dog')
  .map(dog => dog.name);

console.log(dogNames);

使用高阶函数，return 一个对象值，如果另一个值是 true (JavaScript)

Using a higher order function, return one object value if another value is true (JavaScript)

javascript

arrays

object

higher-order-functions