Reduce an array of objects into another array when each object id property is unique [duplicate]

Question

I have a javascript array that looks like this

var array = [{
        id: 1,
        quantity: 2
    },
    {
        id: 2,
        quantity: 1
    },
    {
        id: 1,
        quantity: 5
    }
]

In the above code snippet two objects has same id id:1. If id of two or more objects are same in the array. I want them to be converted into single object and the quantity property of all the object with that particular id id:1 gets accumulated. So the response array should look like this.

var resArray = [{
        id: 1,
        quantity: 7
    },
    {
        id: 2,
        quantity: 1
    }
]

stackoverflow.com/questions/58692417/…

bakar_dev
– bakar_dev

2020-10-21 06:49:01 +00:00
Commented Oct 21, 2020 at 6:49 — bakar_dev
– bakar_dev, Commented Oct 21, 2020 at 6:49

Derek Wang · Accepted Answer · 2020-10-21 06:44:53Z

2

Using Array.reduce, you can group the array by id key value and can sum the quantities of same id.

const array = [{
    id: 1,
    quantity: 2
  },
  {
    id: 2,
    quantity: 1
  },
  {
    id: 1,
    quantity: 5
  }
];

const reducedArr = array.reduce((acc, cur) => {
  acc[cur.id] ? acc[cur.id].quantity += cur.quantity : acc[cur.id] = cur;
  return acc;
}, {});

const output = Object.values(reducedArr);
console.log(output);

answered Oct 21, 2020 at 6:44

Derek Wang

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1 Comment

kazi nur hossain tipu Over a year ago

thanks a lot. well that's perfect. though i was wondering if there is anyway possible to directly recuce the array into result array(acc being an empty array instead of empty object).

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