前端小白的学习之路(ES6 三)

Set集合

size

let s = new Set()
let s2 = new Set(['大事儿', '小事儿', '好事儿', '坏事儿'])
const num = s2.size
console.log(num)   //  4

add

let s = new Set()
let s2 = new Set(['大事儿', '小事儿', '好事儿', '坏事儿'])
s2.add('喜事儿')
console.log(s2)  

delete

let s = new Set()
let s2 = new Set(['大事儿', '小事儿', '好事儿', '坏事儿'])
s2.delete('坏事儿')
console.log(s2)

has

let s = new Set()
let s2 = new Set(['大事儿', '小事儿', '好事儿', '坏事儿'])
const isHas = s2.has('好事儿')
console.log(isHas)  // true

clear

let s = new Set()
let s2 = new Set(['大事儿', '小事儿', '好事儿', '坏事儿'])
 s2.clear()
console.log(s2)  //  Set(0) {size: 0}

Set应用

// 1.数组去重
const arr = [1, 2, 3, 4, 5, 3, 2, 1, 6]
const result1 = [...new Set(arr)]
console.log(result1)   //  [1, 2, 3, 4, 5, 6]

  // 2.数组取交集
const arr = [1, 2, 3, 4, 5, 3, 2, 1, 6]
const arr2 = [4, 5, 6, 5, 6]
const result2 = [...new Set(arr)].filter(item => new Set(arr2).has(item))
console.log(result2)  // [4, 5, 6]

// 3.数组并集
const arr = [1, 2, 3, 4, 5, 3, 2, 1, 6]
const arr2 = [4, 5, 6, 5, 6]
// 先合并arr和arr2，再去重转化为数组
const result3 = [...new Set([...arr, ...arr2])]
console.log(result3)   // [1, 2, 3, 4, 5, 6]

// 4.数组差集
const arr = [1, 2, 3, 4, 5, 3, 2, 1, 6]
const arr2 = [4, 5, 6, 5, 6]
// arr里面的元素，arr2有哪些没有的
const result4 = [...new Set(arr)].filter(item => !(new Set(arr2).has(item)))
console.log(result4)  //   [1, 2, 3]