Combine value with same date in multidimensional array in Javascript

May 18, 2022

I have one array which has two values one date and an amount but there is the same date with a different value at a different index so I need to merge those values into the same date in a multidimensional javascript array

current array

var arry = [
['2021-05-01',100], 
['2021-05-02',300], 
['2021-05-03',200], 
['2021-05-01',150],
['2021-05-02',300], 
['2021-05-01',600],
['2021-05-04',120]
]

Expected Result Array

var arry = [
['2021-05-01',850], 
['2021-05-02',600], 
['2021-05-03',200], 
['2021-05-04',120]]

Can anybody help? I really appreciate any help you can provide.

>Solution :

Here is a solution using reduce. I’m creating an object grouped by date and taking the values array of it

var arry = [['2021-05-01',100], ['2021-05-02',300], ['2021-05-03',200], ['2021-05-01',150],['2021-05-02',300], ['2021-05-01',600],['2021-05-04',120]]

const res = Object.values(arry.reduce((acc,[date,val])=> {
    acc[date] = acc[date] || [date,0]
  acc[date][1]+=val
  return acc
},{}))

console.log(res)