Object.fromEntries

Object.fromEntries() 方法把键值对列表转换为一个对象。

语法

语法：

Object.fromEntries(entries);

类型声明：

interface Iterator<T, TReturn = any, TNext = undefined> {
  // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
  next(...args: [] | [TNext]): IteratorResult<T, TReturn>;
  return?(value?: TReturn): IteratorResult<T, TReturn>;
  throw?(e?: any): IteratorResult<T, TReturn>;
}

interface Iterable<T> {
  [Symbol.iterator](): Iterator<T>;
}

interface ObjectConstructor {
  fromEntries<T = any>(entries: Iterable<readonly [PropertyKey, T]>): { [k: string]: T };

  fromEntries(entries: Iterable<readonly any[]>): any;
}

参数说明：

参数	说明	类型
entries	可实现可迭代协议的可迭代对象（例如 Array、Map 等）	iterable

返回值：

返回一个由该迭代对象条目提供对应属性的新对象。

方法说明

Object.fromEntries() 方法接收一个键值对的列表参数，并返回一个带有这些键值对的新对象。这个迭代参数应该是一个能够实现 @@iterator 方法的的对象，返回一个迭代器对象。它生成一个具有两个元素的类数组的对象，第一个元素是将用作属性键的值，第二个元素是与该属性键关联的值。

Object.fromEntries() 执行与 Object.entries() 互逆的操作。

代码示例

基本用法

const obj = { x: 42, y: 50 };
const entries = Object.entries(obj);
// -> [['x', 42], ['y', 50]];

const result = Object.fromEntries(entries);
// -> { x: 42, y: 50 }

转换 Map 为 Object

const map1 = new Map([
  ['big', 'small'],
  [1, 0],
]);
const geek = Object.fromEntries(map1);
console.log(geek);
// Output: { 1: 0, big: "small" }

const map2 = new Map([
  ['Geek1', 'Intern'],
  ['stipend', 'Works basis'],
]);
const geek1 = Object.fromEntries(map2);
console.log(geek1);
// Output: { Geek1: "Intern", sitipend: "Works basis" }

转换 Array 为 Object

const arr1 = [
  ['big', 'small'],
  [1, 0],
  ['a', 'z'],
];
const geek = Object.fromEntries(arr1);
console.log(geek);
// Output: { 1: 0, big: "small", a: "z" }

const arr2 = [
  ['Geek1', 'Intern'],
  ['stipend', 'Works basis'],
];
const geek1 = Object.fromEntries(arr2);
// Output: { Geek1: "Intern", stipend: "Works basis" }

其他转换

const params = 'type=Get_the Value&geekno=34&paid=10';
const searchParams = new URLSearchParams(params);

console.log(Object.fromEntries(searchParams));
// Output: { type: "Get_ Value", geekno: "34", paid: "10" }

const object1 = { val1: 112, val2: 345, val3: 76 };
const object2 = Object.fromEntries(Object.entries(object1).map(([key, val]) => [key, val * 3]));
console.log(object2);
// Output: { val1: 336, val2: 1035, val3: 228 }

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