原数据：

var data = [
            {"name": "小明","age": "4","birthday": "5-1"},
            {"name": "小黄","age": "4","birthday": "5-1"},
            {"name": "小红","age": "4","birthday": "5-3"},
        ]

希望整理后得到：

var newArr = [
            {
                "birthday":"5-1",
                "detailList":"[ {'name':'小明','age':'4'} , {'name':'小黄','age':'4'}]"
            },
            {
                "birthday":"5-3",
                "detailList":"[ {'name':'小红','age':'4'}]"
            }
        ]; 

我的思路；data数组第0项直接push（birthday+detailList）整个到新数组newArr，但从第1项就要开始去newArr比较birthday，如果birthday相同，就只用push（detailList），如果不同就push { birthday+detailList }

遇到问题：重复打印了一些数据

我的代码：`var data = [

        {"name": "小明","age": "4","birthday": "5-1"},
        {"name": "小黄","age": "4","birthday": "5-1"},
        {"name": "小红","age": "4","birthday": "5-3"},
    ]
    
    //[希望得到]
    // var newArr = [
    //     {
    //         "birthday":"5-1",
    //         "detailList":"[ {'name':'小明','age':'4'} , {'name':'小黄','age':'4'}]"
    //     },
    //     {
    //         "birthday":"5-3",
    //         "detailList":"[ {'name':'小红','age':'4'}]"
    //     }
    // ]; 
    
    
    var arr = []; //存放新数组
    for (var i = 0; i < data.length; i++) {
        //读取每条数据的日期
        var resBirthday = data[i].birthday;
        
        //当日期相同,只要传这个
        var valDetailList = {
            "name": data[i].name,
            "age": data[i].age
        }
        
        //当日期没有相同的,就新建一个Item
        var valItem = { 
            "birthday": '',
            "detailList": []
        }
        valItem.birthday = resBirthday;
        valItem.detailList.push(valDetailList);
        
        //第0个不需要比较
        if (i == 0) {
            arr.push(valItem);
        } 
        //第1个就要开始找新数组arr相同的日期
        else{
            for (var k = 0; k < arr.length; k++) {
                if (resBirthday == arr[k].birthday) {
                    arr[k].detailList.push(valDetailList);
                } 
                else{
                    arr.push(valItem);
                }
            }
        }
    }
    console.log(arr);`