常见的数组方法

常见的数组方法

1, push:在数组最后面添加

let arr = [1, 2, 3, 4, 5]
arr.push(6)
console.log(arr); //=>[1, 2, 3, 4, 5, 6]

2，unshift：在数组最前面添加

let arr = [1, 2, 3, 4, 5]
arr.unshift(0)
console.log(arr); //=>[0, 1, 2, 3, 4, 5]

3, pop: 删除数组最后一项

let arr = [1, 2, 3, 4, 5]
arr.pop()
console.log(arr); //=>[1, 2, 3, 4]

4, shift: 删除数组第一项

let arr = [1, 2, 3, 4, 5]
arr.shift()
console.log(arr); //=>[2, 3, 4，5]

5, reverse: 翻转数组

let arr = [1, 2, 3, 4, 5]
arr.reverse()
console.log(arr); //=>[5，4, 3, 2, 1]

6, splice：第一个参数：从第几个开始删除；第二个参数：删除几个；后面的：添加的是什么

let arr = [1, 2, 3, 4, 5]
arr.splice(2, 2, 2, 2)
console.log(arr); //=>[1, 2, 2, 2, 5]

7, forEach: 循环遍历，相当于for循环,第一个参数当前项，第二个参数是当前项的索引值，第三个参数表示数组本身

let arr = [1, 2, 3, 4, 5]
arr.forEach((item, index) => {
console.log(item, index); //=>0,1    1,2   2,3   3,4   4,5
})

8, filter: 找出满足条件的，放到一个新数组中

let arr = [1, 2, 3, 4, 5]
let a = arr.filter(item => item > 2)
console.log(a); //=>[3, 4, 5]

9, some: 查找数组，有一个满足即为true

let arr = [1, 2, 3, 4, 5]
let a = arr.some(item => item > 2)
console.log(a); //=>true

10, every: 遍历数组，全部满足为true

let arr = [1, 2, 3, 4, 5]
let a = arr.every(item => item > 2)
console.log(a); //=>false

11, map: 遍历数组，把计算结果在重新装一个新数组中

let arr = [1, 2, 3, 4, 5]
let a = arr.map(item => item + 2)
console.log(a); //=>[3, 4, 5, 6, 7]

12, find: 找出第一个满足的数值

let arr = [1, 2, 3, 4, 5]
let a = arr.find(item => item > 2)
console.log(a); //=>3

13, findIndex: 找出第一个满足的索引值

let arr = [1, 2, 3, 4, 5]
let a = arr.findIndex(item => item > 2)
console.log(a); //=>2

14, includes : 查看数组中是否存在此元素

let arr = [1, 2, 3, 4, 5]
let a = arr.includes(2)
console.log(a); //=>true

15, slice（m， n）: 选中第m+1个到第n个之间的数

let arr = [1, 2, 3, 4, 5]
let a = arr.slice(1, 3)
console.log(a) //=>[2, 3]