Question

35

How to merge duplicates in an array of objects and sum a specific property?

rated 0 times [ 36] [ 1] / answers: 1 / hits: 18303 / 8 Years ago, sun, july 10, 2016, 12:00:00

I have this array of objects:

var arr = [

    {

        name: 'John',

        contributions: 2

    },

    {

        name: 'Mary',

        contributions: 4

    },

    {

        name: 'John',

        contributions: 1

    },

    {

        name: 'Mary',

        contributions: 1

    }

];

... and I want to merge duplicates but sum their contributions. The result would be like the following:

var arr = [

    {

        name: 'John',

        contributions: 3

    },

    {

        name: 'Mary',

        contributions: 5

    }

];

How could I achieve that with JavaScript?

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briannar

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answered 8 Years ago admin · Accepted Answer

You could use a hash table and generate a new array with the sums, you need.

var arr = [{ name: 'John', contributions: 2 }, { name: 'Mary', contributions: 4 }, { name: 'John', contributions: 1 }, { name: 'Mary', contributions: 1 }],

    result = [];



arr.forEach(function (a) {

    if (!this[a.name]) {

        this[a.name] = { name: a.name, contributions: 0 };

        result.push(this[a.name]);

    }

    this[a.name].contributions += a.contributions;

}, Object.create(null));



console.log(result);