添加的是同一个对象的地址,所以无论改哪个数组内对象的值,另一个数组内对象的值也会被更改
a = [{name : '小红'}] b1 = [ ...a ] b2 = [] b2.push( a[0] ) // b1 = [{name : '小红'}] // b2 = [{name : '小红'}] a[0].name = '小兰’ // b1 = [{name : '小兰'}] // b2 = [{name : '小兰'}] b1[0].name = '小绿’ // a = [{name : '小绿'}] // b2 = [{name : '小绿'}] b2[0].name = '小五’ // a = [{name : '小五'}] // b1 = [{name : '小五'}]