Group array of objects by multiple properties with Lodash

Question

is possible with lodash library group elements by 2 properties? I have array of objects like this:

[{
   id: 1,
   amount: 2000,
   date: "2018-01-31T00:00:00.000Z"
},{
   id: 2,
   amount: 3000,
   date: "2017-07-31T00:00:00.000Z"
},{
   id: 3,
   amount: 6000,
   date: "2018-01-31T00:00:00.000Z"
},{
   id: 4,
   amount: 7000,
   date: "2017-01-31T00:00:00.000Z"
},{
   id: 5,
   amount: 5000,
   date: "2017-03-31T00:00:00.000Z"
},{
   id: 6,
   amount: 3000,
   date: "2018-02-22T00:00:00.000Z"
},{
   id: 7,
   amount: 4500,
   date: "2017-01-31T00:00:00.000Z"
}]

My goal is group objects in array by:

year
month

Purpose of that grouping is that I need in result order these objects' sum of amount by newest. So for that reason I need distinguish January 2017 from January 2018. It should be 2 different groups.

I am not sure if my approach is correct so I write here my required output:

[
  3000, // sum of 2018-2
  8000, // sum of 2018-1
  3000 // sum of 2017-7
  5000 // sum of 2017-3
  11500 // sum of 2017-1
]

I tried following command but it doesn't work and give me error:

  let xxx = _(data)
    .groupBy(function(i) {
      new Date(i.date).getFullYear()
    })
    .groupBy(function(i) {
      new Date(i.date).getMonth()
    })
    .map(x => x.amount)
    .sum()
    .orderBy('date').value();

Can you help me to fix it ? Thanks.

Simply _.groupBy(data, x => x.date.slice(0, 7))...

georg
– georg

2018-03-19 12:40:33 +00:00
Commented Mar 19, 2018 at 12:40 — georg
– georg, Commented Mar 19, 2018 at 12:40

Vikramaditya · Accepted Answer · 2018-03-19 15:54:47Z

2

You can just concat your year and month with groupBy and use it.

var grouped = _.groupBy(data, function(i) {
  return new Date(i.date).getFullYear()+'-'+new Date(i.date).getMonth()
})

var resultUnsorted = _.map(t, (val, key) => ({key: key, val: val.reduce((p, c) => c.amount + p, 0) }));

then sort using _.orderBy

const output = _.orderBy(resultUnsorted, 'key');

you can write your custom sort function using the behaviour you want.

edited Mar 19, 2018 at 15:54

answered Mar 19, 2018 at 12:41

Vikramaditya

5,5947 gold badges37 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

stack001 stack001 Over a year ago

this works thanks, but when I grouped objects and sum amount, how should I call orderBy ? there is no anymore date property :/

Vikramaditya Over a year ago

date key will be present which you can use for _.orderBy, since we are not mutating date.

stack001 stack001 Over a year ago

But I also need to call map function to calculate amount, so when I join orderBy on the end of chain like this: *.orderBy(function() {console.log(o)}) It will be print just number value which I calculated in map ... so I am not able order by some property of previous object.

Collectives™ on Stack Overflow

Group array of objects by multiple properties with Lodash

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related