数组--其他

 1.复制数组--(Array.from(), 剩余参数)

//array.from()---将类数组对象转成数组

let a=[1,4,6,3,4];
let arr1=Array.from(a);
arr1.push(9)
let arr2=[...a];
arr2.push(8)
console.log(a,arr1,arr2)

//[1, 4, 6, 3, 4] [1, 4, 6, 3, 4, 9] [1, 4, 6, 3, 4, 8]

2.Array.from()和Array.of()的用法

//Array.from--将类数组（有length的对象）转化为数组
//Array.of---将一组值转成数组

let a='apple';
console.log(Array.from(a));
//["a", "p", "p", "l", "e"]

console.log(Array.of('aa','bb','cc'))
//["aa", "bb", "cc"]

 3.arr.reverse()--颠倒数组顺序

//改变原数组
let arr=[1,2,3,4,5,6];
arr.reverse();
console.log(arr)

// [6, 5, 4, 3, 2, 1]

4.arr.sort()--数组元素排序

//改变原数组
let arr=[1,6,3,8,4,6,2];
arr.sort();
console.log(arr)
//[1, 2, 3, 4, 6, 6, 8]

5.数组转字符串

//不改变原数组
let arr=[1,2,3,4,5,6];
arr.join(',');
console.log(arr)
console.log(arr.join(','))

// [1, 2, 3, 4, 5, 6]
//1,2,3,4,5,6