js 深拷贝

var arr = [1,2,3,4,5]
var arr2 = copyArr(arr)
function copyArr(arr) {
    let res = []
    for (let i = 0; i < arr.length; i++) {
     res.push(arr[i])
    }
    return res
}

var arr = [1,2,3]
var arr2 = arr.slice(0)
arr[2] = 5

var arr = [1,2,3]
var arr2 = arr.concat()
arr[2] = 5

    ES 6
var arr = [1,2,3,4,5]
var [ ...arr2 ] = arr
arr[2] = 5

转换成json再转换成对象实现对象的深拷贝

var obj = {
  name: 'F',
  sex: 'm',
  old: '11'
}
var obj2 = JSON.parse(JSON.stringify(obj))