Combine an array of values inside array of similar objects which has matching key value pair using JS

Question

I have the following object:

  a = [
{id: 1, comp: 'ans', stat: 'www', value: ['1', '2']},
{id: 2, comp: 'qsn', stat: 'xxx', value: ['a', 'b']},
{id: 3, comp: 'ans', stat: 'yyy', value: ['3', '4']},
{id: 4, comp: 'qsn', stat: 'zzz' ,value: ['c', 'd']}
]

I wanted the best possible way to combine the value array inside of the objects where the key comp matches and the other properties that do not match have the property of the first element intact and concat only the values array. The output I want to achieve in the above scenario is :

[
{id: 1, comp: 'ans', stat: 'www', value: ['1', '2', '3', '4']},
{id: 2, comp: 'qsn', stat: 'xxx', value: ['a', 'b', 'c', 'd']}
]

Search for "Group array of objects by property javascript", that will help you create two arrays. To merge, do something like group.reduce((o1, o2) => ({ ...o1, value: o1.value.concat(o2.value) })) — user3297291
– user3297291, Commented Aug 25, 2020 at 11:03

Ele · Accepted Answer · 2020-08-25 11:31:48Z

2

You can group the objects by comp using the function Array.prototype.reduce and the function Object.values to extract the grouped objects.

const a = [{id: 1, comp: 'ans', stat: 'www', value: ['1', '2']},{id: 2, comp: 'qsn', stat: 'xxx', value: ['a', 'b']},{id: 3, comp: 'ans', stat: 'yyy', value: ['3', '4']},{id: 4, comp: 'qsn', stat: 'zzz' ,value: ['c', 'd']}],
      result = Object.values(a.reduce((a, {comp, value, ...rest}) => {
        (a[comp] || (a[comp] = {...rest, comp, value: []})).value.push(...value);
        return a;
      }, {}));

console.log(result);

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

edited Aug 25, 2020 at 11:31

answered Aug 25, 2020 at 11:02

Ele

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1 Comment

Ele Over a year ago

@vivek-jain the css is to expand the console, don't remove it.

Praveen Bhusal · Accepted Answer · 2021-03-30 04:28:45Z

2

I think a more readable approach is necessary

const a = [{
        id: 1,
        comp: 'ans',
        stat: 'www',
        value: ['1', '2']
    },
    {
        id: 2,
        comp: 'qsn',
        stat: 'xxx',
        value: ['a', 'b']
    },
    {
        id: 3,
        comp: 'ans',
        stat: 'yyy',
        value: ['3', '4']
    },
    {
        id: 4,
        comp: 'qsn',
        stat: 'zzz',
        value: ['c', 'd']
    }
]

const result = [];

for (let aChild of a) {
    const sameComp = result.find(res => res.comp === aChild.comp);
    if (sameComp) {
        sameComp.value = sameComp.value.concat(aChild.value);
    } else {
        result.push(aChild);
    }
}

console.log(result);

answered Mar 30, 2021 at 4:28

Praveen Bhusal

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