js 使用for循环过滤对象数组

Question

    let objList = [
        {name:'tom',age:12},
        {name:'jack',age:33},
        {name:'zio',age:12},
        {name:'lolo',age:89},
        {name:'robin',age:16},
        ]
    
    let ageList = [12,16];
    let getData = objList.filter((item)=>{
        return ageList.includes(item.age)
    });
    
    console.log(getData)

如上所示，最后打印出来的数据是年龄为12 16的元素 ，想请教各位大佬，如果只是用for循环的方法如何才能过滤对象数组得到想要的数据呢？

Answer 1

var newArr=[];
for(var i=0;i<objList.length;i++)
  ageList.indexOf(objList[i].age)!=-1&&(newArr.push(objList[i]));

Answer 2

这标题取的，完全跟算法无关好吧，就是基础判断而已

let getData = [];
for (let i = 0; i < objList.length; i++) {
  let item = objList[i];
  if (ageList.includes(item.age)) {
    getData.push(item);
  }
}
console.log(getData)

而filter可以简化成

 let getData = objList.filter(({age}) => ageList.includes(age));

2段代码的结果一样，根本没必要写for循环，反正上线都要编译成es5

Answer 3

如果不考虑顺序问题可以先把数据源从Array转成Map.Array<?>，再使用过滤条件逐一取出想要的数据：

let objList = [
    {name:'tom',age:12},
    {name:'jack',age:33},
    {name:'zio',age:12},
    {name:'lolo',age:89},
    {name:'robin',age:16},
];
let map = {};
objList.forEach(item => (map[item.age] = map[item.age]||[]).push(item));
console.log(map);

let ret = [];
[12,16].forEach(item => {
    map[item] && Array.prototype.push.apply(ret, map[item]);
});
console.log(ret);