数组的深拷贝方法

• 1.for 循环

let arr = [1,2,3,4,5];
let arr1 = [];
for(let i = 0;i < arr.length;i++){
    arr1[i] = arr[i];
}
arr1.push(6);
console.log(arr1);//[1, 2, 3, 4, 5, 6]

• 2.concat();

let arr = [1,2,3,4,5];
let arr2 = [].concat(arr);
arr2.push(6);
console.log(arr2);//[1, 2, 3, 4, 5, 6]

• 3. ... 扩展运算符

let arr = [1,2,3,4,5];
let arr3 = [...arr];
let [...arr4} = arr;
arr3.push(6);
arr4.push(6);
console.log(arr3);//[1, 2, 3, 4, 5, 6]
console.log(arr4);//[1, 2, 3, 4, 5, 6]

... 拓展

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

let [a,b,...c] = arr;
console.log(c);//[3, 4, 5]

function fn1(...arg){
        //arguments
       console.log(arg);//[1, 2, 3, 4, 5, 6, 7, 8]
}
fn1(1,2,3,4,5,6,7,8);

数组的操作方法

• 1.数组排序 .sort();

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

• 2.flat();
  将多维数组展开成一维数组，通常用于数据处理

let arr = [[1,2,3,[4,5,6,[7,8[9,0]]],[11,12,13]]];
console.log(arr.flat(1));//[1, 2, 3, Array(4), Array(3)]
console.log(arr.flat(2));//[1, 2, 3, 4, 5, 6, Array(3), 11, 12, 13]
console.log(arr.flat(Infinity));[1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 11, 12, 13]
//参数写几，就展开几层
//展开所有层，参数用Infinity

• 3.forEach();
  用于遍历数组中的每一个元素

let arr = [1,2,3,4,5,6,7,8,9];
arr.forEach(value,index,array) =>{
    console.log(value,index,array);
    //第一个参数当前元素值
    //第二个参数当前元素的索引值
    //第三个参数原数组
    *参数名不固定，但是参数顺序固定*
}