map()对数组的每个元素进行一定操作（映射）后，会返回一个新的数组，map()不会对空数组进行检测。map()不会改变原数组
varoldArr = [{first_name:"Colin",last_name:"Toh"},{first_name:"Addy",last_name:"Osmani"},{first_name:"Yehuda",last_name:"Katz"}];
functiongetNewArr(){
returnoldArr.map(function(item,index){
item.full_name = [item.first_name,item.last_name].join(" ");
returnitem;
});
}
console.log(getNewArr());
