How to get array of arrays by grouping ids

Question

I have an array:

let ar = [{
   asst: 1,
   v: 'b'
 }, {
   emp: 4
 }, {
   journal_id: 3
 }, {
   asst: 4
 }, {
   asst: 1,
   v: 'a'
 }, {
   asst: 1,
   v: 'c'
 }, {
   journal_id: 3
 }, {
   journal_id: 3
 }]

I want an array that has asst and journal_id as array of arrays and emp as just an object in the array that has array of asst and journal_id. Like this:

[[{asst:1, v: 'a'}, {asst:1, v: 'b'},{asst:1, v: 'c'}], [{asst:4}], [{journal_id:3}, {journal_id:3}, {journal_id:3}], {emp:4}]

I have tried this:

let ar = [{
    asst: 1,
    v: 'b'
}, {
    emp: 4
}, {
    journal_id: 3
}, {
    asst: 4
}, {
    asst: 1,
    v: 'a'
}, {
    asst: 1,
    v: 'c'
}, {
    journal_id: 3
}, {
    journal_id: 3
}]
let asstArray = [],
    journalArray = [],
    fullArray = [];

for (let i = 0; i < ar.length; i++) {
    debugger
    if (ar[i].asst) {
        let contains = false;
        for (let j = 0; j < asstArray.length; j++) {
            for (let k = 0; k < asstArray[j].length; k++) {
                if (asstArray[j][k].asst == ar[i].asst) {
                    contains = true;
                    let d = asstArray[j][k];
                }
            }
            if (contains) {
                asstArray[j].push(ar[i]);
            }
        }
        if (!contains) {
            asstArray.push([ar[i]]);
        }
    } else if (ar[i].journal_id) {
        let contains = false;
        for (let j = 0; j < journalArray.length; j++) {
            for (let k = 0; k < journalArray[j].length; k++) {
                if (journalArray[j][k].journal_id == ar[i].journal_id) {
                    contains = true;
                }
            }
            if (contains) {
                journalArray[j].push(ar[i]);
            }
        }
        if (!contains) {
            journalArray.push([ar[i]]);
        }
    }
}
fullArray.push(asstArray);
fullArray.push(journalArray);
console.log(fullArray, "Full")

JS Fiddle

jo_va · Accepted Answer · 2019-01-31 14:24:07Z

3

Here is a succint way to do it with reduce and Object.values. Also, the keys to check are declared in the initial value to the reduce function.

By using ES6 desctructuring, you can then rebuild the array you want at the end, with emp, out of the inner arrays.

With emp in the array:

const ar = [
  { asst: 1, v: 'b' },
  { emp: 4 },
  { journal_id: 3 },
  { asst: 4 },
  { asst: 1, v: 'a' },
  { asst: 1, v: 'c' },
  { journal_id: 3 },
  { journal_id: 3 }
];

const result = Object.values(ar.reduce((accum, e) => {
  Object.keys(accum).forEach(k => {
    if (k in e) accum[k].push(e);
  });
  return accum;
}, { asst: [], journal_id: [], emp: [] }));

console.log(result);

With emp outside the inner array:

const ar = [
  { asst: 1, v: 'b' },
  { emp: 4 },
  { journal_id: 3 },
  { asst: 4 },
  { asst: 1, v: 'a' },
  { asst: 1, v: 'c' },
  { journal_id: 3 },
  { journal_id: 3 }
];

let result = ar.reduce((accum, e) => {
  Object.keys(accum).forEach(k => {
    if (k in e) accum[k].push(e);
  });
  return accum;
}, { asst: [], journal_id: [], emp: [] });

const { emp, ...otherProps } = result;
result = [...Object.values(otherProps), emp[0]];

console.log(result);

edited Jan 31, 2019 at 14:24

answered Jan 31, 2019 at 13:33

jo_va

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5 Comments

Le guy Over a year ago

i don't want emp to be inside an array. i want it to be just an object

jo_va Over a year ago

Yes, updated, emp is now out: [ [ { "asst": 1, "v": "b" }, { "asst": 4 }, { "asst": 1, "v": "a" }, { "asst": 1, "v": "c" } ], [ { "journal_id": 3 }, { "journal_id": 3 }, { "journal_id": 3 } ], { "emp": 4 } ]

Le guy Over a year ago

thank you but i dont know how many objects i will have like emp. so it won't work. im sorry for un accepting your answer

jo_va Over a year ago

Well, I can edit and put emp back in the array, the code will be even shorter, you now have both versions, and very short code

jo_va Over a year ago

@Le guy, You should reedit your question then to reflect that

Nina Scholz · Accepted Answer · 2019-01-31 13:33:19Z

2

You could combine the values of the wanted grouping keys to a single key and group by this value.

Objects without grouping keys are pushed to the result set directly.

var array = [{ asst: 1, v: 'b' }, { emp: 4 }, { journal_id: 3 }, { asst: 4 }, { asst: 1, v: 'a' }, { asst: 1, v: 'c' }, { journal_id: 3 }, { journal_id: 3 }], keys = ['asst', 'journal_id'],
    keys = ['asst', 'journal_id'],
    result = array.reduce((hash => (r, o) => {
        if (keys.some(k => k in o)) {
            var key = keys.map(k => o[k]).join('|');
            if (!hash[key]) {
                r.push(hash[key] = []);
            }
            hash[key].push(o);
        } else {
            r.push(o);
        }
        return r;
    })({}), []);

console.log(result);

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

edited Jan 31, 2019 at 13:33

answered Jan 31, 2019 at 13:17

Nina Scholz

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10 Comments

Le guy Over a year ago

i don't want emp to be inside an array. i want it to be just an object

Nina Scholz Over a year ago

yould you have more than one object with emp?

Le guy Over a year ago

yes i will have more than one emp and others like emp that aren't asst or journal_id

Le guy Over a year ago

i dont want those that aren't asst or journal_id to be an array inside the array

Nina Scholz Over a year ago

do you need a special order as well?

|

HMR · Accepted Answer · 2019-01-31 13:41:04Z

2

You can reduce the array in a Map and then create a new array with the Map values:

const data = [{"asst":1,"v":"b"},{"emp":4},{"journal_id":3},{"asst":4},{"asst":1,"v":"a"},{"asst":1,"v":"c"},{"journal_id":3},{"journal_id":3}];


const grouped = data.reduce(
  (result,item)=>{
    //key is item.asst or item.jornal_id or other
    const key = item.asst || item.journal_id || 'other';
    //set result(key) with empty array or existing array and conat new item
    return result.set(key,(result.get(key)||[]).concat(item));
  },new Map()
);
//get other values or empty array if they don't exist:
const others = grouped.get('other') || [];
//remove others if they exist:
grouped.delete('other');

//log array from Map values
console.log(others.concat([...grouped.values()]));

edited Jan 31, 2019 at 13:41

answered Jan 31, 2019 at 13:18

HMR

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2 Comments

Le guy Over a year ago

i don't want emp to be inside an array. i want it to be just an object

HMR Over a year ago

@Leguy Updated answer.

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