es6学习随笔

Array(9).fill(null) ;   //[null,null,null,null,null,null,null,null,null]

深克隆

》》数组X.slice()

var obj=Array(9).fill(null)
var b=obj.slice()
b[1] = "X"

b    //(9) [null, "X", null, null, null, null, null, null, null]
obj //(9) [null, null, null, null, null, null, null, null, null]

We call .slice() to copy the squares array instead of mutating the existing array. Jump ahead a section to learn why immutability is important.

》》对象 Object.assign

var player = {score: 1, name: 'Jeff'};
var newPlayer = Object.assign({},player,{score:2})
newPlayer  //{score: 2, name: "Jeff"}

player //{score: 1, name: "Jeff"}