数组映射 ,重新整理,配合return,返回一个新数组，没有return，相当于forEach()

arr.map(val,index,arr) 

let arr = [
    {title:'name',age:'10'},
    {title:'aaa',age:'10'},
    {title:'aaa',age:'10'},
    {title:'aaa',age:'10'},
]
let map = arr.map((val,index,arr) => {
    let json = {}
    json.t = val.title;
    json.a = val.age;
    return json;
})
console.log(map);

Run Code:

[ { t: 'name', a: '10' },
 
{ t: 'aaa', a: '10' },
 
{ t: 'aaa', a: '10' },
 
{ t: 'aaa', a: '10' } ]