Filtering of the array of objects

August 11, 2022

I’m trying to filter the array:

const arr = [
{
  id: '1',
  modifiedTime: '2022-08-11T12:30:36.191Z',
  modifiedUser: 'test'
},
{
  id: '2',
  modifiedTime: '2022-08-11T12:30:36.191Z',
  modifiedUser: 'test'
},
{
  id: '2',
  modifiedTime: '2022-09-12T12:30:36.191Z',
  modifiedUser: 'test'
},
{
  id: '3',
  modifiedTime: '2022-08-11T12:30:36.191Z',
  modifiedUser: 'test'
},
];

to get results:

const arr = [
{
  id: '1',
  modifiedTime: '2022-08-11T12:30:36.191Z',
  modifiedUser: 'test'
},
{
  id: '2',
  modifiedTime: '2022-09-12T12:30:36.191Z',
  modifiedUser: 'test'
},
{
  id: '3',
  modifiedTime: '2022-08-11T12:30:36.191Z',
  modifiedUser: 'test'
},
];

so, I need to filter the array in that way to stay with objects without duplicates, when an object has a duplicate, it should get only one with the largest modifiedTime.

I was trying to do this in that way:

arr.reduce((arr, el) => (((arr.find(({id}) => el.id === id)) || arr.push(el)), arr), [])

but in this way, it returns to me an array without objects with duplicates id but modifiedTime is not the largest.

Maybe someone will be able to suggest it to me?

>Solution :

You have 3 cases :

If the item is not in the array, simply push it
If the item is already but has a smaller time : don’t do anything
If the item is already but has an higher time : replace the item with the new one

This can be done using the js splice method

const arr = [{
    id: '1',
    modifiedTime: '2022-08-11T12:30:36.191Z',
    modifiedUser: 'test'
  },
  {
    id: '2',
    modifiedTime: '2022-08-11T12:30:36.191Z',
    modifiedUser: 'test'
  },
  {
    id: '2',
    modifiedTime: '2022-09-12T12:30:36.191Z',
    modifiedUser: 'test'
  },
  {
    id: '3',
    modifiedTime: '2022-08-11T12:30:36.191Z',
    modifiedUser: 'test'
  },
];

console.log(
  arr.reduce((acc, curr) => {
    const index = acc.findIndex(x => x.id === curr.id)
    if(index === -1) acc.push(curr)
    else {
      if(new Date(acc[index].modifiedTime) < new Date(curr.modifiedTime))
        acc.splice(index, 1, curr)
    }
    
    return acc
  }, [])
)