Question

63

Group By and Sum using Underscore/Lodash

rated 0 times [ 69] [ 6] / answers: 1 / hits: 39759 / 10 Years ago, wed, july 30, 2014, 12:00:00

I have JSON like this:

[

  {

     platformId: 1,

     payout: 15,

     numOfPeople: 4

  },

  {

     platformId: 1,

     payout: 12,

     numOfPeople: 3



  },

  {

     platformId: 2,

     payout: 6,

     numOfPeople: 5



  },

  {

     platformId: 2,

     payout: 10,

     numOfPeople: 1

  },



]

And I want to Group it by platformId with sum of payout and numOfPeople.

I.e. in result I want JSON like this:

[

  1: {

     payout: 27,

     numOfPeople: 7

   },



  2: {

     payout: 16,

     numOfPeople: 6

  }

]

I tried to use underscore.js's _.groupBy method, and it groups fine, but how I can get the SUM of objects properties values like I demonstrated above?

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

gregorio

Add To Favorites

Follow

Total Points: 362

Total Questions: 95

Total Answers: 93

Location: Puerto Rico

Member since Sun, Jun 27, 2021

3 Years ago

answered 10 Years ago albert · Accepted Answer

You can do this without Underscore:

var result = data.reduce(function(acc, x) {

  var id = acc[x.platformId]

  if (id) {

    id.payout += x.payout

    id.numOfPeople += x.numOfPeople

  } else {

    acc[x.platformId] = x

    delete x.platformId

  }

  return acc

},{})

But why would you want an object with numeric keys? You could convert it back to a collection:

var toCollection = function(obj) {

  return Object.keys(obj)

    .sort(function(x, y){return +x - +y})

    .map(function(k){return obj[k]})

}



toCollection(result)

Note that objects are mutated, so you may to clone them first if you want to maintain the original data.