Concatenate and aggregate json object data with node.js

Question

I generate the following json in my Node application:

    [ { id: 1,
        name: 'user1',
        sport: 'athletics',
        medal_count: '1' 
      },
      { id: 1,
        name: 'user1',
        sport: 'tennis',
        medal_count: '2' 
      },
      { id: 2,
        name: 'user2',
        sport: ['football'],
        medal_count: '2' 
      }
    ]

I'd now like to concatenate users so that they appear as a single object with the sport listed in an array and the medal_count aggegrated for the user. The above json would look like this:

    [ { id: 1,
        name: 'user1',
        sport: [
          'athletics',
          'tennis'
        ],
        medal_count: '3' 
      },
      { id: 2,
        name: 'user2',
        sport: 'football',
        medal_count: '2' 
      }
    ]

How is this done? Am I correct in thinking this should be done with a map reduce function?

Smart Manoj · Accepted Answer · 2019-05-08 16:49:07Z

2

Edited

let input = [{
  id: 1,
  name: 'user1',
  sport: 'athletics',
  medal_count: '1'
},
  {
    id: 1,
    name: 'user1',
    sport: 'tennis',
    medal_count: '2'
  },
  {
    id: 2,
    name: 'user2',
    sport: 'football',
    medal_count: '2'
  }
];

let grouped = {};
input.forEach(({id, name, sport, medal_count}) => {
  grouped[id] = grouped[id] || {id, name, sport: [], medal_count:0};
  if (!grouped[id].sport.includes(sport))
    grouped[id].sport.push(sport);
  grouped[id].medal_count = `${(+grouped[id].medal_count)+ (+medal_count)}`;
});
grouped = Object.values(grouped);

console.log(grouped);

edited May 8, 2019 at 16:49

Smart Manoj

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answered May 8, 2019 at 15:52

junvar

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Comments

Manuel Spigolon · Accepted Answer · 2019-05-08 15:58:43Z

1

Yes, you are right:

'use strict';

const data = [{
  id: 1,
  name: 'user1',
  sport: 'athletics',
  medal_count: '1',
},
{
  id: 1,
  name: 'user1',
  sport: 'tennis',
  medal_count: '2',
},
{
  id: 2,
  name: 'user2',
  sport: 'football',
  medal_count: '2',
}];


const out = data.reduce((accumulator, item) => {
  if (accumulator[item.id]) {
    const group = accumulator[item.id];
    if (Array.isArray(group.sport)) {
      group.sport.push(item.sport);
    } else {
      group.sport = [group.sport, item.sport];
    }
    group.medal_count = `${(+group.medal_count) + (+item.medal_count)}`;
  } else {
    accumulator[item.id] = item;
  }
  return accumulator;
}, {});

console.log(JSON.stringify(out, null, 2));

Note that you are using numbers as strings for medal_count

answered May 8, 2019 at 15:58

Manuel Spigolon

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4 Comments

runnerpaul Over a year ago

Thanks. How do I ensure all sport objects are arrays and not just the ones with more than 1 sport?

runnerpaul Over a year ago

I edited the code sample to ensure all sport objects are arrays, even if they only contain one value. Otherwise, thanks for the help.

Manuel Spigolon Over a year ago

Yeah, in that case, the if(Array.isArray is no more necessary

runnerpaul Over a year ago

Ah yes. I see this works: ``` const out = data.reduce((accumulator, item) => { if (accumulator[item.id]) { const group = accumulator[item.id]; group.sport.push(item.sport); group.medal_count = ${(+group.medal_count) + (+item.medal_count)}; } else { accumulator[item.id] = item; item.sport = [item.sport] } return accumulator; }, {}); console.log(JSON.stringify(out, null, 2)); ```

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