JavaScript merge array objects with the same keys

April 13, 2022

I have an array with several objects some have the same keys (Question and QuestionId), for example:

    var jsonData = [
            {
                Question: "Was the training useful?",
                QuestionId: 1,
                myData: [{ name: 'No', value: 1 }] },
            {
                Question: "Was the training useful?",
                QuestionId: 1 ,
                myData: [{ name: 'Yes', value: 1 }]
        }];

How can I combine these objects into one, expected output:

      var jsonData = [
        {
            Question: "Was the training useful?",
            QuestionId: 1,
            myData: [{ name: 'No', value: 1 },
                     { name: 'Yes', value: 1 }] 
          }];

>Solution :

var jsonData = [{
    Question: "Was the training useful?",
    QuestionId: 1,
    myData: [{
      name: 'No',
      value: 1
    }]
  },
  {
    Question: "Was the training useful?",
    QuestionId: 1,
    myData: [{
      name: 'Yes',
      value: 1
    }]
  }
];

const result = Object.values(jsonData.reduce((acc, obj) => {
  if (!acc[obj.QuestionId]) {
    acc[obj.QuestionId] = obj;
  } else {
    acc[obj.QuestionId].myData = acc[obj.QuestionId].myData.concat(obj.myData);
  }
  return acc;
}, {}));

console.log(result);