JavaScript中Set和Map数据结构使用场景详解

// 1  数组去重
const arr = [1, 2, 3, 2, 1];
const set = new Set(arr);
const newArr = Array.from(set); // newArr = [1, 2, 3]
// 2 对象去重
const arr = [{ id: 1 }, { id: 2 }, { id: 1 }, { id: 3 }];
const set = new Set(arr.map(item => item.id));
const newArr = Array.from(set, id => ({ id })); 
// newArr = [{ id: 1 }, { id: 2 }, { id: 3 }]

// 创建一个Map对象
const formData = new Map();
// 添加表单元素的值到Map中
formData.set('username', 'Tom');
formData.set('password', '123456');
// 获取表单元素的值
const username = formData.get('username');// username = Tom
const password = formData.get('password');// password = 123456

const formData = new Map();
formData.set('username', 'Tom');
formData.set('password', '123456');
// 通过get()方法来获取已存储的数据
const username = formData.get('username');// username = Tom
const password = formData.get('password');// password = 123456

const state = new Map();
state.set('loading', false);
state.set('error', null);
// 通过set()方法来更新已存储的数据
state.set('loading', true);
state.set('error', '请求失败');

const list = new Map();
list.set(1, { id: 1, name: 'Tom' });
list.set(2, { id: 2, name: 'Join' });
// 通过get()方法来获取已存储的数据
const item = list.get(1); // item = { id: 1, name: 'Tom' }
const item = list.get(2); // item = { id: 2, name: 'Join' }

const cache = new Map();
cache.set('key1', 'value1');
cache.set('key2', 'value2');
// 通过get()方法来获取已存储的数据
const value = cache.get('key1');// value = value1
const value = cache.get('key2');// value = value2