JSON group by key value to new JSON Javascript

Question

I have been reading some posts which are related to my question, whereas I have not been able to find a proper solution for what I'm trying to do hear.

I have this JSON file that I am obtaining directly from my database via a sql query:

[
    {
        "scenario": "scenario-483d742c-4492-4a4f-95fa-7ccceac8bb18",
        "data": [
            {
                "date": "2018-05-21",
                "price": 14.173041264216105
            }
        ]
    },
    {
        "scenario": "scenario-483d742c-4492-4a4f-95fa-7ccceac8bb18",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
        ]
    }, 
    {
        "scenario": "scenario-c705069f-fa53-4ff3-9f07-3fcbf9dc8d15",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
        ]
    },
    {
        "scenario": "scenario-c705069f-fa53-4ff3-9f07-3fcbf9dc8d15",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
        ]
    },
    {
        "scenario": "scenario-d58bb001-d7ed-4744-8f6c-8377519c7a99",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
        ]
    },
    {
        "scenario": "scenario-d58bb001-d7ed-4744-8f6c-8377519c7a99",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
        ]
    }
]

My objectif is to be able to sort/transform this json object to a new json object which is classified by the scenario, so, something that looks like:

[
    {
        "scenario": "scenario-483d742c-4492-4a4f-95fa-7ccceac8bb18",
        "data": [
            {
                "date": "2018-05-21",
                "price": 14.173041264216105
            },
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
        ]
    },
    {
        "scenario": "scenario-c705069f-fa53-4ff3-9f07-3fcbf9dc8d15",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            },
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }

        ]
    },
    {
        "scenario": "scenario-d58bb001-d7ed-4744-8f6c-8377519c7a99",
        "data": [
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            },  
            {
                "date": "2018-05-22",
                "price": 42.94691197077433
            }
 ]

I have been trying some javascript selfmade functions but I have not obtainend the desired result. This is the last thing I've tried:

 let estructura = [];

    for (var j =0; j<obj.length; j++){
      for (var i=0; i<estructura.length; i++){
        if(obj[j]['scenario'] == estructura[i]['scenario']){
          estructura[i]['data'].push(obj[j]['data'])
        } else {
          console.log("no match, we add the scenario to estructura")
          estructura.push(
            {
              scenario:obj[j]['scenario'],
              data: []
            })
        }
      }

    }

Thank you

You are grouping by, not "filtering" or "classify by " I would say ? — Ole EH Dufour
– Ole EH Dufour, Commented Jul 10, 2018 at 8:49
I have posted the function I was using. And yes, it is group by — Guillem Puig comerma
– Guillem Puig comerma, Commented Jul 10, 2018 at 8:50
Maybe this is what you need: stackoverflow.com/questions/21776389/javascript-object-grouping — Anastasios Selmani
– Anastasios Selmani, Commented Jul 10, 2018 at 8:55
please look at the following meta.stackoverflow.com/questions/261592/… — LaCodeM
– LaCodeM, Commented Oct 26, 2021 at 13:34

CertainPerformance · Accepted Answer · 2018-07-10 08:56:24Z

9

You can achieve this easily with built-in functions like reduce. Iterate over the input, grouping into an object indexed by scenario, creating a object with a data array if the scenario doesn't exist yet, and push to that array:

const input=[{"scenario":"scenario-483d742c-4492-4a4f-95fa-7ccceac8bb18","data":[{"date":"2018-05-21","price":14.173041264216105}]},{"scenario":"scenario-483d742c-4492-4a4f-95fa-7ccceac8bb18","data":[{"date":"2018-05-22","price":42.94691197077433}]},{"scenario":"scenario-c705069f-fa53-4ff3-9f07-3fcbf9dc8d15","data":[{"date":"2018-05-22","price":42.94691197077433}]},{"scenario":"scenario-c705069f-fa53-4ff3-9f07-3fcbf9dc8d15","data":[{"date":"2018-05-22","price":42.94691197077433}]},{"scenario":"scenario-d58bb001-d7ed-4744-8f6c-8377519c7a99","data":[{"date":"2018-05-22","price":42.94691197077433}]},{"scenario":"scenario-d58bb001-d7ed-4744-8f6c-8377519c7a99","data":[{"date":"2018-05-22","price":42.94691197077433}]}]

console.log(
  Object.values(input.reduce((a, { scenario, data }) => {
    if (!a[scenario]) a[scenario] = { scenario, data: [] };
    a[scenario].data.push(data[0]);
    return a;
  }, {}))
);

answered Jul 10, 2018 at 8:56

CertainPerformance

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1 Comment

Guillem Puig comerma Over a year ago

Thank you very much

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