Question

187

How can I sum properties from two objects?

rated 0 times [ 188] [ 1] / answers: 1 / hits: 22521 / 7 Years ago, mon, february 27, 2017, 12:00:00

I have multiple JavaScript objects:

{

  a: 12,

  b: 8,

  c: 17

}

and

{

  a: 2,

  b: 4,

  c: 1

}

I need to sum these two object by keys

Result:

{

  a: 14,

  b: 12,

  c: 18

}

Do you have any solutions in JavaScript?
I use Object.keys.map but it's too long because I have like 100 elements in my object.

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desiraeleandrah

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4 Years ago

answered 7 Years ago nikokorbinm · Accepted Answer

You can use reduce for that, below function takes as many objects as you want and sums them by key:

var obj1 = {

  a: 12,

  b: 8,

  c: 17

};



var obj2 = {

  a: 12,

  b: 8,

  c: 17

};



var obj3 = {

  a: 12,

  b: 8,

  c: 17

};





function sumObjectsByKey(...objs) {

  return objs.reduce((a, b) => {

    for (let k in b) {

      if (b.hasOwnProperty(k))

        a[k] = (a[k] || 0) + b[k];

    }

    return a;

  }, {});

}



console.log(sumObjectsByKey(obj1, obj2, obj3));