关于前端:数组的-splice-slice方法

splice 办法

构造1: 
arr.splice(start,deletedCount) 纯删除
从start下标开始,删除几个

构造2: 
arr.splice(start,deletedCount,item) 替换
从start下标开始,删除几个,并在该地位增加item

构造3: 
arr.splice(start,0,item) 纯增加
从start下标开始,删除0个,并在该地位增加item,start开始全副往后挪动

let arr = [1,2,6,7,8];
arr.splice(2,0,3,4,5);//arr = [1,2,3,4,5,6,7,8];

slice 办法

该办法能够从数组中截取指定的字段,返回进去
返回值:返回截取进去的字段,放到新的数组中,不扭转原数组

构造1:
arr.slice(start,end) ;从start下标开始截取,始终到end完结,不包含end

let arr = [0,1,2,3,4,5,6,7];
let newArr = arr.slice(0,3)//newArr = [0,1,2];

构造2:
arr.slice(start) ;从start下标开始截取,始终到最初

let arr = [0,1,2,3,4,5,6,7];
let newArr = arr.slice(2)//newArr = [2，3，4，5，6，7];

构造3:
arr.slice( ) ;全副截取

let arr = [0,1,2,3,4,5,6,7];
let newArr = arr.slice()//newArr = [0,1,2,3,4,5,6,7];