Group array of objects based on array-type key

Question

Having input like the below:

[
  {
    gameId: id_0,
    groups: [1]
  },
  {
    gameId: id_1,
    groups: [2]
  },
  {
    gameId: id_2,
    groups: [1, 2]
  },
  {
    gameId: id_3,
    groups: [3]
  }
]

I would like my reduce to result in an array of objects like:

[
  {
    group: 1,
    data: [
      id_0, id_2 // gameId
    ]
  },
  {
    group: 2,
    data: [
      id_1, id_2
    ]
  },
  {
    group: 3,
    data: [
      id_3
    ]
  }
]

I was able to partially solve this by utilising array indexes. The code I have currently is:

groupByArr = parameter => data => data.reduce((acc, curr) => {
  curr[parameter].forEach(key => {
    if (acc[key]) {
      acc[key].push(curr)
    } else {
      acc[key] = [curr]
    }
  })
  return acc
}, [])

which produces an array of arrays where main array index is the group id:

[
  empty,
  1: [
    id_0, id_2
  ],
  2: [
    id_1, id_2
  ],
  3: [
    id_3
  ]
]

Yosvel Quintero · Accepted Answer · 2019-09-19 08:07:40Z

1

You can use Array.prototype.reduce() combined with Array.prototype.forEach() and Array.prototype.push() to return an Object and finally get the values with Object.values()

Code:

const data = [{gameId: 'id_0',groups: [1]},{gameId: 'id_1',groups: [2]},{gameId: 'id_2',groups: [1, 2]},{gameId: 'id_3',groups: [3]}]
const result = Object.values(data.reduce((acc, {gameId, groups}) => {
  groups.forEach(group => {
    acc[group] = acc[group] || { group, data: [] }
    acc[group].data.push(gameId)
  })
  return acc
}, {}))

console.log(result)

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Sep 19, 2019 at 8:07

answered Sep 19, 2019 at 5:27

Yosvel Quintero

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2 Comments

user0101 Over a year ago

Appreciate your work, thanks for keeping your answer up to date!

Yosvel Quintero Over a year ago

@user0101 glad to help!

user5845598 · Accepted Answer · 2019-09-19 05:28:26Z

0

Let arr be the variable containing data in following format:

[
  empty,
  1: [
    id_0, id_2
  ],
  2: [
    id_1, id_2
  ],
  3: [
    id_3
  ]
]

Then following code might do:-

for(let i=1;i<arr.length;i++){
    arr[i-1] = {group:i,data:arr[i]};
}
arr[arr.length-1] = undefined; // To Prevent Unnecessary Errors
delete arr[arr.length-1]; // To Prevent Unnecessary Errors
arr.length -= -1;

Now arr will be in following format:-

[
  {
    group: 1,
    data: [
      id_0, id_2
    ]
  },
  {
    group: 2,
    data: [
      id_1, id_2
    ]
  },
  {
    group: 3,
    data: [
      id_3
    ]
  }
]

Hope it helps. Tell me if I Misunderstood your question.

answered Sep 19, 2019 at 5:28

user5845598

Comments

Jonas Wilms · Accepted Answer · 2019-09-19 05:30:17Z

0

Use an object as acc, then add objects to it:

  if (acc[key]) {
    acc[key].data.push(curr)
  } else {
     acc[key] = { group: key, data: [curr] };
  }

And finally, turn the returned object into an array:

 const result = Object.values(hash);

answered Sep 19, 2019 at 5:30

Jonas Wilms

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Comments

Janie · Accepted Answer · 2019-09-19 05:34:35Z

0

Try this

const data = [
    {gameId: 'id_0',groups: [1]},
    {gameId: 'id_1',groups: [2]},
    {gameId: 'id_2',groups: [1, 2]},
    {gameId: 'id_3',groups: [3]}
]

const single_id = data.filter(i => i.groups.length === 1)
const multiple_ids = data.filter(i => i.groups.length > 1)
let res = [];
single_id.map(i => {
    let data = {group: i.groups[0], data: [i.gameId]}
    multiple_ids.forEach(o => o.groups.includes(i.groups[0]) && (data.data.push(o.gameId)))
    res.push(data)
})
console.log(res)

answered Sep 19, 2019 at 5:34

Janie

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Comments

Raghuraman Kesavan · Accepted Answer · 2019-09-19 05:46:40Z

0

`let b = [
  {
    gameId: "id_0",
    groups: [1]
  },
  {
    gameId: "id_1",
    groups: [2]
  },
  {
    gameId: "id_2",
    groups: [1, 2]
  },
  {
    gameId: "id_3",
    groups: [3]
  }
];

let d = new Map(); ;
b.forEach(function(a){
    a.groups.forEach(function(a1){
        if(d.get(a1)){
            d.get(a1).push(a.gameId);
        }else{
            d.set(a1, [a.gameId]);
        }
    });
});`

answered Sep 19, 2019 at 5:46

Raghuraman Kesavan

711 silver badge6 bronze badges

Comments

Syed Afzal · Accepted Answer · 2019-09-19 05:58:13Z

0

You should try this one. Using reduce in grouped scenarios is the best thing JavaScript provides us

let arr = [
{
        gameId: "id_0",
        groups: [1]
    },
    {
        gameId: "id_1",
        groups: [2]
    },
    {
        gameId: "id_2",
        groups: [1, 2]
    },
    {
        gameId: "id_3",
        groups: [3]
    }
];


const grouped = arr.reduce((acc, current) => {
    for(let x of current.groups){
        if(!acc[x]) {
            acc[x] = {group: x, data:[current.gameId]}
        } else {
            acc[x].data.push(current.gameId)
        }
    }
    return acc
},{});

console.log(Object.values(grouped))

answered Sep 19, 2019 at 5:58

Syed Afzal

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