jQuery: Grouping object property depending on another property value

Question

I have a array of object that looks like the following.

[
  {"rel_id": 1,"forward_flag": true,"asset_id":5,},
  {"rel_id": 1,"forward_flag": true,"asset_id":8},
  {"rel_id": 1,"forward_flag": false,"asset_id":3},
  {"rel_id": 2,"forward_flag": true,"asset_id":5,},
  {"rel_id": 2,"forward_flag": true,"asset_id":7,},
  {"rel_id": 2,"forward_flag": false,"asset_id":9,}
]

I'm trying to group the object based on the properties rel_id and forward_flag . For those objects whose rel_id and forward_flag are same , I'm trying to create an array of asset_id values and make a new object.

So once processed end result will look like

[
  {"rel_id":1,"forward_flag":true,"asset_id":[5,8]},
  {"rel_id":1,"forward_flag":false,asset_id:[3]},
  ...
]

I have tried to achieve the same using jQuery like this.

preData.forEach(function(item){
   var first = item;
        preData.forEach(function(compare){
            if(compare.rel_id != first.rel_id || compare.forwardFlag!= first.forwardFlag || compare.asset_id != first.assetid) //to make sure same item is not compared
            {
                if(compare.rel_id == first.rel_id && compare.forwardFlag == first.forwardFlag)
                {
                  //do something here
                }
            }
        })

  })

where preData is the array of objects. I'm stuck now, and not clear what to do next. Are there any easier ways to achieve this?

how rel_id and forward_flag are going to be same one is boolean and one is number — RIYAJ KHAN
– RIYAJ KHAN, Commented Mar 24, 2016 at 9:20

gurvinder372 · Accepted Answer · 2016-03-24 09:25:22Z

1

You need to make another object for this,

Using your code

 var newArray = [];
 var rels = {};
 preData.forEach(function(item){    
     var relForward = item.rel_id + "===" + item.forwardFlag;
     if ( !rels[ relForward ] )
     {
        rels[ relForward ] = [];
     }
     rels[ relForward ].push(item);
 });

Now iterate rels to populate final output newArray

 newArray = Object.keys( rels ).map(function(key){
     var item = rels[key][0];
     var assets = rels[key].map(function(value){ return value.asset_id; });
     return { rel_id : item.rel_id, forward_flag: item.forward_flag, asset_id:  assets };
 });

answered Mar 24, 2016 at 9:25

gurvinder372

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Comments

Nina Scholz · Accepted Answer · 2016-03-24 09:20:34Z

In plain Javascript, you can use Array#forEach() and a temporary object for the reference to the new array items.

var array = [{ "rel_id": 1, "forward_flag": true, "asset_id": 5, }, { "rel_id": 1, "forward_flag": true, "asset_id": 8 }, { "rel_id": 1, "forward_flag": false, "asset_id": 3 }, { "rel_id": 2, "forward_flag": true, "asset_id": 5, }, { "rel_id": 2, "forward_flag": true, "asset_id": 7, }, { "rel_id": 2, "forward_flag": false, "asset_id": 9, }],
    grouped = function (array) {
        var r = [];
        array.forEach(function (a) {
            var key = a.rel_id + '|' + a.forward_flag;
            if (!this[key]) {
                this[key] = { rel_id: a.rel_id, forward_flag: a.forward_flag, asset_id: [] };
                r.push(this[key]);
            }
            this[key].asset_id.push(a.asset_id);
        }, {});
        return r;
    }(array);

document.write('<pre>' + JSON.stringify(grouped, 0, 4) + '</pre>');

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