js array copy method

//浅拷贝：

let arr=[1,2,3,4]

let arr2=arr

arr[3]=0

console.log(arr,arr2)

//output: (4) [1, 2, 3, 0] (4) [1, 2, 3, 0]

//深拷贝1：

var arr3=[1,2,3,4]

var arr4=[]

for(var i=0;i<arr.length;i++){

arr4.push(arr3[i])}

console.log(arr4)

//output: (4) [1, 2, 3, 4]

//深拷贝2,slice：

var arr7=[1,2,3,4]

var arr8=arr7.slice(0,4)

arr7[3]=0

console.log(arr7,arr8)

//output: (4) [1, 2, 3, 0] (4) [1, 2, 3, 4]