Set
// set对象示意值得汇合，且每个值得都是惟一的（根本类型）（援用类型只有地址不一样即可）// 申明const s1 = new Set();console.log(typeof s1,s1); // object Set {}// set办法// 增 adds1.add(1);console.log(s1); // Set { 1 }const obj1 = {name:'xuwen'};const obj2 = {name:'xuwen'};s1.add(obj1);s1.add(obj2); // 阐明援用类型 地址不一样 值是能够一样的console.log(s1); // Set { 1, { name: 'xuwen' }, { name: 'xuwen' } }// 删 delete clearconsole.log(s1.add(2)); // Set { 1, { name: 'xuwen' }, { name: 'xuwen' }, 2 } 返回s1console.log(s1.delete(1)); // true 返回布尔值 删除胜利返回trueconsole.log(s1); // Set { { name: 'xuwen' }, { name: 'xuwen' }, 2 }s1.clear();console.log(s1); // Set {}// 查 hass1.add(2);s1.add('a');s1.add([1,23]);console.log(s1); // Set { 2, 'a', [ 1, 23 ] }console.log(s1.has(2)); // true// 迭代console.log(s1.keys()); // [Set Iterator] { 2, 'a', [ 1, 23 ] }console.log(s1.values()); // [Set Iterator] { 2, 'a', [ 1, 23 ] }console.log(s1.entries()); // [Set Entries] { [ 2, 2 ], [ 'a', 'a' ], [ [ 1, 23 ], [ 1, 23 ] ] }s1.forEach((value,key,s1) => { console.log(value,key);});// 2 2// a a// [ 1, 23 ] [ 1, 23 ]// set属性// size set长度console.log(s1.size); // 3// set实例// 超级典型的就是数组去重 在数组章节有过实例const arr1 = [1,2,4,5,6,4,5,6];const newArr1 = [...new Set(arr1)];console.log(newArr1); // [ 1, 2, 4, 5, 6 ]// 数组去重的变异实例 字符串去重let str1 = "xxwenxxxsdwexx";let newStr1 = [...new Set(str1)].join('')console.log(newStr1); // xwensd// 汇合类型 并集 交加 差集// set并集const s2 = new Set(['x','w','e']);const s3 = new Set(['x','w','y']);const s4 = new Set([...s2,...s3]);console.log(s4); // Set { 'x', 'w', 'e', 'y' }// set 交加const s5 = new Set([...s2].filter(item => s3.has(item)))console.log(s5); // Set { 'x', 'w' }// set 差集const s6 = new Set([...s2].filter(item => !s3.has(item)))console.log(s6);const s7 = new Set([...s3].filter(item => !s2.has(item)));const s8 = new Set([...s6,...s7]);console.log(s8); // Set { 'e', 'y' }
Map
// 在ES6之前 对象中的key值只能是字符串 不论是数值类型还是援用类型都会转换成字符串// 在es6中 引入了map类型 他能够让key值为任何类型而不必去转换// map属性 size 示意map的长度const map = new Map();console.log(map.size); // 0// map的办法// 增 setconst arr1 = [1,2,4];const obj1 = {name:'xuwen'};const num1 = 2020;const str1 = "xuwen";const n1 = null;const u1 = undefined;map.set(arr1,'x') .set(obj1,'u') .set(num1,'w') .set(str1,'e') .set(n1,'n') .set(u1,'u');console.log(map,map.size);// Map {// [ 1, 2, 4 ] => 'x',// { name: 'xuwen' } => 'u',// 2020 => 'w',// 'xuwen' => 'e',// null => 'n',// undefined => 'u'// } 6// 删 delete clearconsole.log(map.delete(arr1)); // trueconsole.log(map);// clear会革除所有的key和值 就不演示了// 查 has getconsole.log(map.has(u1)); // trueconsole.log(map.get(num1)); // w get是返回key对应的值let year = 2007;console.log(map.get(year)); // undefined 如果没有就返回undefined// 迭代console.log(map.keys()); // [Map Iterator] { { name: 'xuwen' }, 2020, 'xuwen', null, undefined }console.log(map.values()); // [Map Iterator] { 'u', 'w', 'e', 'n', 'u' }console.log(map.entries());// [Map Entries] {// [ { name: 'xuwen' }, 'u' ],// [ 2020, 'w' ],// [ 'xuwen', 'e' ],// [ null, 'n' ],// [ undefined, 'u' ]// }