How to loop through an Array of objects and add key value pairs into another array of objects based on duplicate entries

Question

I am trying to loop through an array of objects with multiple dates and other data. I want the dates to be stored in the start and the rest of the data to be stored in an array data[]. In cases the date is similar for any two objects, I want to push all the data(except for the date) into the data[]

Original data:

[{

    start: "2019-08-23",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Lecture",

  },

  {

    start: "2019-08-25",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Tutorial",

  },

  {

    start: "2019-08-25",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Lecture",

  }]

Expected Output:

[{

    start: "2019-08-23",

    data: [{ title: "Week 5 Dispensing Tutorial 3 Quiz", type: "Lecture" }]

  },

  {

    start: "2019-08-25",

    data: [{ title: "Week 5 Dispensing Tutorial 3 Quiz", type: "Tutorial" }, {title: "Week 5 Dispensing Tutorial 3 Quiz", type: "Lecture" }]

  }]

I have tried the following code, but it doesnt handle the duplication:

var result[] = ITEMS.map(ITEMS => ({
      start: ITEMS.start,
      data: [
        {
          title: ITEMS.title,
          type: ITEMS.type
        }
      ]
    }));

Jose Nuno · Accepted Answer · 2019-08-22 13:21:03Z

const input = [{

    start: "2019-08-23",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Lecture",

  },

  {

    start: "2019-08-25",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Tutorial",

  },

  {

    start: "2019-08-25",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Lecture",

  }];

  const output = [];
  input.forEach(v => {
      if (!output.map(o => o.start).includes(v.start)) { //If there are no duplicates
          output.push({
              start: v.start,
              data: [{
                   title: v.title,
                   type: v.type
              }]
          });
      }
      else { //If there are duplicates
          for (let i = 0; i < output.length; i++) {
              if (output[i].start === v.start) { //Find the duplicated one
                  output[i].data.push({
                      title: v.title,
                      type: v.type
                  });
                  break;
              }
          }
      }
  });

  console.log(output);

Mohammad Ali Rony · Accepted Answer · 2019-08-22 13:23:58Z

try this

var arrray =[{

    start: "2019-08-23",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Lecture",

  },

  {

    start: "2019-08-25",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Tutorial",

  },

  {

    start: "2019-08-25",

    title: "Week 5 Dispensing Tutorial 3 Quiz ",

    type: "Lecture",

  }];
  
  let newArrray =[];
  
  arrray.forEach(function(element)
  {
    let dOjb = newArrray.find(x => x.start === element.start);
    if(dOjb)
    {
      dOjb.data.push({
          'title': element.title,
          'type': element.type
        })
    }
    else
    {
      newArrray.push(
      {
        'start': element.start,
        data: [
        {
          'title': element.title,
          'type': element.type
        }
      ]}
      );
    }

});
  
  console.log(newArrray);

Hardik Shah · Accepted Answer · 2019-08-22 14:14:02Z

You can try below logic:

var data = [{ start: "2019-08-23", title: "Week 5 Dispensing Tutorial 3 Quiz ", type: "Lecture", }, { start: "2019-08-25", title: "Week 5 Dispensing Tutorial 3 Quiz ", type: "Tutorial", }, { start: "2019-08-25", title: "Week 5 Dispensing Tutorial 3 Quiz ", type: "Lecture", }]

var nData = {};

(data || []).forEach( e => {
  nData[e.start] = {
    data : (nData[e.start] ? nData[e.start].data.push({title: e.title, type: e.type}) && nData[e.start].data : [{title: e.title, type: e.type}])
  }
});

var modifiedData = Object.keys(nData).map(k => {
  return {
    start: k,
    data: nData[k].data 
  }
})

console.log(modifiedData)

Another way, Let's create `array` directly:

var data = [{ start: "2019-08-23", title: "Week 5 Dispensing Tutorial 3 Quiz ", type: "Lecture", }, { start: "2019-08-25", title: "Week 5 Dispensing Tutorial 3 Quiz ", type: "Tutorial", }, { start: "2019-08-25", title: "Week 5 Dispensing Tutorial 3 Quiz ", type: "Lecture", }]

var nData = [];

(data || []).forEach( e => {
  var i = (index = nData.findIndex(d => d.start === e.start)) >=0 ? index : nData.length;
  nData[i] = {
    start: e.start,
    data : (nData[i] && nData[i].data ? nData[i].data.push({title: e.title, type: e.type}) && nData[i].data : [{title: e.title, type: e.type}])
  }
});

console.log(nData);

Hope this helps!

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How to loop through an Array of objects and add key value pairs into another array of objects based on duplicate entries

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Another way, Let's create `array` directly:

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3 Answers 3

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Another way, Let's create array directly:

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Another way, Let's create `array` directly: