Insert Objects with similar keys into an array, is the key exists

Question

This might be a basic issue that I am unable to fix. I have an initial array values received from an API something like this:

const primaryArray = [
    {
    startDate: '01-01-2021',
    endDate: '11-01-2021',
    refs: [
        {
        refId: "FL013",
                year: "2021"
      }
    ]
  },
  {
    startDate: '01-02-2021',
    endDate: '28-02-2021',
    refs: [
        {
        refId: "FL013",
                year: "2021"
      }
    ]
  },
  {
    startDate: '03-05-2020',
    endDate: '10-06-2020',
    refs: [
        {
        refId: "FL013",
                year: "2020"
      }
    ]
  },
  {
    startDate: '25-03-2019',
    endDate: '25-04-2019',
    refs: [
        {
        refId: "FL013",
                year: "2019"
      }
    ]
  }
];

Since two of the objects of year 2021 share the same reference key as 'FL013', I want to convert them into the form as this with all objects separated out from array:

{
    2021: { 
    'year': 2021, 
    'refIds': ['FL013', 'FL013'], 
    'duration': { 
      'FL013': [
        {
          startDate: '01-01-2021',
          endDate: '11-01-2021'
        }, 
        {
          startDate: '01-02-2021',
          endDate: '28-02-2021',
        }
       ]
     }
    }
},
{
    2020: { year: 2020, 'refIds': ['FL013'], 'duration': { 'FL013': {
                                               startDate: '03-05-2020',
                                               endDate: '10-06-2020',
                                             }
          }
},
{
    2019: { year: 2019, 'refIds': ['FL013'], 'duration': { 'FL013': {
                                               startDate: '25-03-2019',
                                               endDate: '25-04-2019',
                                             }
          }
}

I tried to use JS reduce for the same, but the array creation for year with two dates objects keeps throwing me an error.

This is what I tried to achieve so far:

const flatArray = primaryArray && primaryArray.reduce(
(acc, {startDate, endDate, refs}, currentIndex) => {

  const year = refs && refs[0] && refs[0].year;
  const refId = refs && refs[0] && refs[0].refId;
            
   if (
        year &&
        refId &&
        startDate &&
        endDate &&
        !Object.prototype.hasOwnProperty.call(acc, year)
      ) {
           acc[year] = {
               year,
               refIds: [refId],
               duration: {
                           [refId]: {
                             startDate,
                             endDate,
                         },
               },
           };
        } else {
            if (year) {
                acc[year].refIds.push(refId);
                acc[year]['duration'][refId] = {
                  startDate,
                  endDate,
                };
              }
            }
   return acc;
},{});

I modified my above code using two approaches to achieve the exact result: first, to push the dates object as received in the accumlator

acc[year]['duration'][refId].push({ startDate, endDate }).

This throws error:

Uncaught TypeError: acc[year].duration[refId].push is not a function

or second, direct apply [] notation (which I understand is not applicable).

Here is the working link for the same: https://onecompiler.com/javascript/3wwzz3f4s

Any help to resolve the same, highly appreciated.

Your playcode link doesn't have any code... but when I tested this on my machine the output looked good and no errors... — Kinglish
– Kinglish, Commented May 9, 2021 at 17:13
@JohnTyner This works but does not return me the format I require. I have updated my working code link — program_bumble_bee
– program_bumble_bee, Commented May 9, 2021 at 17:22

zb22 · Accepted Answer · 2021-05-09 17:45:30Z

You can do something like this with Array.prototype.reduce():

const primaryArray = [
    {
    startDate: '01-01-2021',
    endDate: '11-01-2021',
    refs: [
        {
        refId: "FL013",
                year: "2021"
      }
    ]
  },
  {
    startDate: '01-02-2021',
    endDate: '28-02-2021',
    refs: [
        {
        refId: "FL013",
                year: "2021"
      }
    ]
  },
  {
    startDate: '03-05-2020',
    endDate: '10-06-2020',
    refs: [
        {
        refId: "FL013",
                year: "2020"
      }
    ]
  },
  {
    startDate: '25-03-2019',
    endDate: '25-04-2019',
    refs: [
        {
        refId: "FL013",
                year: "2019"
      }
    ]
  }
];

const res = primaryArray.reduce((acc, {refs, startDate, endDate}) => {
  if(!acc[refs[0].year]) {   
    acc[refs[0].year] = {
      year: refs[0].year,
      refIds: [refs[0].refId],
      duration: {
        [refs[0].refId]: {
          startDate: startDate,
          endDate: endDate
        }
      }
    }
  } else {
    acc[refs[0].year].refIds.push(refs[0].refId);
    acc[refs[0].year].duration = {
      [refs[0].refId]: [
        {...acc[refs[0].year].duration[refs[0].refId]},
        {
          startDate: startDate,
          endDate: endDate
        }
      ]

    }
  }

  return acc;
}, {})

console.log(res);

Kinglish · Accepted Answer · 2021-05-09 17:48:36Z

Another option is to test to see if it's already an array, if not then create it. typeof acc[year]['duration'][refId] !== '[object Array]'

const flatArray = primaryArray && primaryArray.reduce(
(acc, {startDate, endDate, refs}, currentIndex) => {

  const year = refs && refs[0] && refs[0].year;
  const refId = refs && refs[0] && refs[0].refId;


            
   if (
        year &&
        refId &&
        startDate &&
        endDate &&
        !Object.prototype.hasOwnProperty.call(acc, year)
      ) {
           acc[year] = {
               year,
               refIds: [refId],
               duration: {
                           [refId]: {
                             startDate,
                             endDate,
                         },
               },
           };
        } else {
            if (year) {
                acc[year].refIds.push(refId);
                if (acc[year]['duration'][refId] && typeof acc[year]['duration'][refId] !== '[object Array]') {
                    acc[year]['duration'][refId] = [acc[year]['duration'][refId]]
                }

                acc[year]['duration'][refId].push({
                  startDate,
                  endDate,
                })
              }
            }
   return acc;
},{});

bel3atar · Accepted Answer · 2021-05-09 17:49:54Z

const primaryArray = [{
    startDate: '01-01-2021',
    endDate: '11-01-2021',
    refs: [{
      refId: 'FL013',
      year: '2021',
    }, ],
  },
  {
    startDate: '01-02-2021',
    endDate: '28-02-2021',
    refs: [{
      refId: 'FL013',
      year: '2021',
    }, ],
  },
  {
    startDate: '03-05-2020',
    endDate: '10-06-2020',
    refs: [{
      refId: 'FL013',
      year: '2020',
    }, ],
  },
  {
    startDate: '25-03-2019',
    endDate: '25-04-2019',
    refs: [{
      refId: 'FL013',
      year: '2019',
    }, ],
  },
];

const result = primaryArray.reduce((acc, cur) => {
  const {
    startDate,
    endDate,
    refs: [{
      refId,
      year
    }],
  } = cur;
  const entry = acc[year];
  const yearExistsAlready = entry !== undefined;
  if (yearExistsAlready) {
    entry.refIds.push(refId);
    const duration = entry.duration[refId];
    const durationExistsAlready = duration !== undefined;
    if (durationExistsAlready) entry.duration[refId].push({
      startDate,
      endDate
    });
    else entry.duration = {
      refId: {
        startDate,
        endDate
      }
    };
  } else {
    acc[year] = {
      year,
      refIds: [refId],
      duration: {
        [refId]: [{
          startDate,
          endDate
        }],
      },
    };
  }
  return acc;
}, {});
console.log(result)

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