sort会修改原数组 

利用数组api ——> sort来进行排序

var person = [{name:"Rom",age:12},{name:"Bob",age:22},{name:"Ma",age:5},{name:"Tony",age:25}]

person.sort((a,b)=>{ return a.age-b.age})//升序

person.sort((a,b)=>{ return b.age-a.age})//降序