Get rid of duplicates in array of objects

Question

I'm trying to get rid of duplicates in array of objects. I want my code linear so I'm using hashtable:

output = Array.from(new Set(output.map(e => e.company)))
  .map(company => { return output.find(e => e.company === company) })

This code works properly for this array of objects:

let output = [
  { company: 'sony'},
  { company: 'sony'},
  { company: 'apple'}
]

but thing is that I want to reuse this code so I would like to move it to function which would take array output and company string. I don't know how to do that, I tried like this:

const uniq = (array, key) => {
  return Array.from(new Set(array.map( e => e[key] )))
    .map(key => { return array.find(e => e[key] === key) })
}

but this return array of two undefined.

---

Also second thing is that it's pretty complicated code for such trivial task. Isn't there some easier way to do same without losing performance?

Answer 1

This one-liner works with arbitrary objects, not necessarily key:value pairs:

let uniqBy = (a, key) => [...new Map(a.map(x => [x[key], x]).reverse()).values()];

//

let data = [
    {company: 'sony', more: 1},
    {company: 'apple', more: 1},
    {company: 'sony', more: 2},
    {company: 'sony', more: 3},
    {company: 'apple', more: 3},
]

console.log(uniqBy(data, 'company'))

If you don't care about the order of the result, you can also skip .reverse().

Answer 2

You could map the unique values and create a new object.

const 
    unique = (array, key) => Array.from(new Set(array.map(o => o[key])), value => ({ [key]: value }));

var output = [{ company: 'sony'}, { company: 'sony'}, { company: 'apple'}];

console.log(unique(output, "company"));