How to sum values in an array of objects in javascript

Question

I have an array of objects, like so:

[
    {
        Daypart: "G_POSTPEAK",
        day_of_week: "Monday",
        uplift: 1
    },
    {
        Daypart: "A_BREAKFAST",
        day_of_week: "Thursday",
        uplift: 1
    },
    {
        Daypart: "C_DAYTIME",
        day_of_week: "Sunday",
        uplift: 2
    },
    {
        Daypart: "G_POSTPEAK",
        day_of_week: "Monday",
        uplift: 2
    },
]

I have only shown a sample of objects in the array, I am working with a lot more. They all have the specified properties, the daypart property could be one of 8 values and the day of week value could be one of 7 (days of the week).

I want to return the sum of the uplift value for all the objects that have the same daypart and day_of_week value.

So the above should return something like:

{
    G_POSTPEAK_Monday: {
        Daypart: "G_POSTPEAK",
        day_of_week: "Monday",
        uplift: 3
    },
    A_BREAKFAST_Thursday: {
        Daypart: "A_BREAKFAST",
        day_of_week: "Thursday",
        uplift: 1
    },

    C_DAYTIME_Sunday: {
        Daypart: "C_DAYTIME",
        day_of_week: "Sunday",
        uplift: 2
    }
}

Appreciate any help

Answer 1

The following function can be used. I have used ES6. The function takes inputs which will be your input object.

 const sumIt = (inputs) => { const result = {}; inputs.forEach((input) => { const key = `${input.Daypart}_${input.day_of_week}`; if (key in result) { result[key].uplift = result[key].uplift + input.uplift; } else { result[key] = { ...input }; } }); return result; };

Answer 2

You can use ES6 reduce function to perform the sum in one line instead of using foreach.

 let array = [ { Daypart: "G_POSTPEAK", day_of_week: "Monday", uplift: 1 }, { Daypart: "A_BREAKFAST", day_of_week: "Thursday", uplift: 1 }, { Daypart: "C_DAYTIME", day_of_week: "Sunday", uplift: 2 }, { Daypart: "G_POSTPEAK", day_of_week: "Monday", uplift: 2 }, ]; const totalUplift = array.reduce((acc, array) => acc + array.uplift, 0); console.log(totalUplift);

Answer 3

You can use array#reduce to group data based on the Daypart and day_of_week in an object accumulator.

 let data = [ { Daypart: "G_POSTPEAK", day_of_week: "Monday", uplift: 1 }, { Daypart: "A_BREAKFAST", day_of_week: "Thursday", uplift: 1 }, { Daypart: "C_DAYTIME", day_of_week: "Sunday", uplift: 2 }, { Daypart: "G_POSTPEAK", day_of_week: "Monday", uplift: 2 }], result = data.reduce((r,o) => { let key = `${o.Daypart}_${o.day_of_week}`; r[key] = r[key] || {...o, uplift: 0}; r[key].uplift += o.uplift; return r; },{}); console.log(result);

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

Answer 4

A somewhat more functional version, using reduce like several other solutions.

 const combine = inputs => Object .values ( inputs .reduce ((a, {Daypart, day_of_week, uplift}) => { const key = `${Daypart}|${day_of_week}` return {...a, [key]: ({ Daypart, day_of_week, uplift: (a[key] && a[key].uplift || 0) + uplift })} }, {}) ) let inputs = [ {Daypart: "G_POSTPEAK", day_of_week: "Monday", uplift: 1}, {Daypart: "A_BREAKFAST", day_of_week: "Thursday", uplift: 1}, {Daypart: "C_DAYTIME", day_of_week: "Sunday", uplift: 2}, {Daypart: "G_POSTPEAK", day_of_week: "Monday", uplift: 2}, ] console .log ( combine (inputs) )

Answer 5

You can use loadash package to perform this in optimized way...

let _ = require('lodash');
let arrays = [
  {
    'name':'monday',
    vaue:1
  },
 {
    'name':'monday',
    vaue:2
 },
 {
    'name':'tuesday',
    vaue:3
 },
 {
   'name':'wednesday',
   vaue:11
 },
 {
   'name':'wednesday',
   vaue:11
 },
]

let newarray = _(arrays).groupBy("name").map(   (name) => ({
   name: name,
   value0: _.sumBy(name, 'vaue')
 }))
 .value()
console.log(newarray);