数组方法

.push

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];

从尾部添加元素
arr.push(1, 2)
[1, 2, 3, 4, 5, 6, 7, 8, 99, 1, 2]

.unshift

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];
从头部添加元素
arr.unshift(1, 2);
[1, 2, 1, 2, 3, 4, 5, 6, 7, 8, 99]

arr.pop() 从最后删除一个元素,返回值是删除的元素。

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];
arr.pop()
let a = arr.pop()
console.log(arr);   [1, 2, 3, 4, 5, 6, 7, 8]
console.log(a);     99

arr.shift() 从前面删除一个元素，返回值是删除的元素

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];
arr.shift();
console.log(arr);   [2, 3, 4, 5, 6, 7, 8, 99]
let a = arr.shift() 
console.log(a)      1

arr.splice(i,n) 删除从i(索引值)开始之后的那个元素.返回值是删除的元素

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];
arr.splice(0,2);   //3,4,5,6,7,8,99 去掉了两个
console.log(arr);               //[3, 4, 5, 6, 7, 8, 99]
console.log(arr.splice(0,3));   //[1, 2, 3]

arr.concat() 连接两个数组返回值为链接后的新数组

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];
let arr1 = ['数字', '字母']
let arr3 = ['true', 'false']
let arr4 = [111, 222, 33]
let arr2 = arr1.concat(arr, arr3, arr4)
console.log(arr2);  //['数字', '字母', 1, 2, 3, 4, 5, 6, 7, 8, 99, 'true', 'false', 111, 222, 33]

arr.split() 将字符串转化为数组

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 99];
let string = "这是一个字符串";
let arr1 = string.split('');
console.log(arr1);              //['这', '是', '一', '个', '字', '符', '串']
let string1 = '1-2-3-4-5'
console.log(string1.split('-'));    //['1', '2', '3', '4', '5']
console.log(string.split('',3));    //['这', '是', '一']
console.log(string);                //这是一个字符串

字符串

arr.split() 将字符串转化为数组

let string = "这是一个字符串";
let arr1 = string.split('');
console.log(arr1);              //['这', '是', '一', '个', '字', '符', '串']
let string1 = '1-2-3-4-5'
console.log(string1.split('-'));    //['1', '2', '3', '4', '5']
console.log(string.split('',3));    //['这', '是', '一']
console.log(string);                //这是一个字符串

.concat() 拼接字符串

var source = "hello";
var target = " web";
var aaa = source.concat(target);   //连接两个或多个字符串
console.log(aaa);   //hello web

...

var source = "hello";
var target = "123";
console.log(source, ...target); //hello 1 2 3