Convert JSON array with same key value

Question

I have a array in this form

[
        {
            "time": "2017-09-14 02:44 AM",
            "artist": "Sam",
            "message": "message 1",
            "days": 0
        },
         {
            "time": "2017-09-14 02:44 AM",
            "artist": "Jerry",
            "message": "message 2",
            "days": 2
        },
        {
            "time": "2017-09-14 02:44 AM",
            "artist": "Sam",
            "message": "message 3",
            "days": 4
        },
         {
            "time": "2017-09-14 02:49 AM",
            "artist": "Jerry",
            "message": "message 5",
            "days": 2
        },
         {
            "time": "2017-09-14 02:59 AM",
            "artist": "Sam",
            "message": "message 7",
            "days": 10
        },
        {
            "time": "2017-09-14 02:59 AM",
            "artist": "Sam",
            "message": "message 5",
            "days": 10
        },
]

and i need output as like this

[{
    artist:"Sam",
    data : [
        {message:"message 1" , days: 0},
        {message:"message 3" , days: 4},
        {message:"message 7" , days: 10},
        {message:"message 5" , days: 10}
    ]
},
{
    artist:"Jerry",
    data : [
        {message: "message 2", days: 2},
        {message: "message 5", days: 2}
    ]
}]

Any help from you is highly appreciated.

here is the code i have tried,

  var obj = {};
    data.map(function(item){
        if(angular.isDefined(obj.artist) && obj.artist === item.artist){
            obj.data.push({message: item.message, days:item.days })
        }else{
            obj.artist = item.artist;
            obj.data = [];
            obj.data.push({message: item.message, days:item.days })
        }
    });
   console.log(obj);

But it creates a single JSON object.

Answer 1

Try this Array#reduce function

1. push created obj with the new array.
2. Then create the array only with artist value.

3. Then apply to check artist value already present in array or not using Array#indexOf()>0 .

4. is there .just push the other object to exist data array

5. Array#index used find the position of the object presented in new array

 var arr = [ { "time": "2017-09-14 02:44 AM", "artist": "Sam", "message": "message 1", "days": 0 }, { "time": "2017-09-14 02:44 AM", "artist": "Jerry", "message": "message 2", "days": 2 }, { "time": "2017-09-14 02:44 AM", "artist": "Sam", "message": "message 3", "days": 4 }, { "time": "2017-09-14 02:49 AM", "artist": "Jerry", "message": "message 5", "days": 2 }, { "time": "2017-09-14 02:59 AM", "artist": "Sam", "message": "message 7", "days": 10 }, { "time": "2017-09-14 02:59 AM", "artist": "Sam", "message": "message 5", "days": 10 }, ] var res = arr.reduce(function(a,b){ var f =a.map(i=> i.artist) if(f.indexOf(b.artist) > 0){ a[f.indexOf(b.artist)].data.push({message:b.message,days:b.days}) }else{ a.push({artist:b.artist, data:[{message:b.message,days:b.days}]}) } return a; },[]) console.log(res) 

Answer 2

You could use a hash table for same artist and collect the data with it.

 var data = [{ time: "2017-09-14 02:44 AM", artist: "Sam", message: "message 1", days: 0 }, { time: "2017-09-14 02:44 AM", artist: "Jerry", message: "message 2", days: 2 }, { time: "2017-09-14 02:44 AM", artist: "Sam", message: "message 3", days: 4 }, { time: "2017-09-14 02:49 AM", artist: "Jerry", message: "message 5", days: 2 }, { time: "2017-09-14 02:59 AM", artist: "Sam", message: "message 7", days: 10 }, { time: "2017-09-14 02:59 AM", artist: "Sam", message: "message 5", days: 10 }], hash = Object.create(null), result = data.reduce(function (r, a) { if (!hash[a.artist]) { hash[a.artist] = { artist: a.artist, data: [] }; r.push(hash[a.artist]); } hash[a.artist].data.push({ message: a.message, days: a.days }); return r; }, []); console.log(result); 

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