Return an array of names

Question

I am struggling with returning an array of owner names from a given array of dog objects.

I know the reduce method is required in this instance, but I can't quite figure out how to proceed

function getPugOwners(dogs) {
  /*
    This function takes an array of dog objects and returns an array of the names of all the owners.
    E.g. [
      {name: 'Beatrice', breed: 'Lurcher', owner: 'Tom'},
      {name: 'Max', breed: 'Pug', owner: 'Izzi'},
      {name: 'Poppy', breed: 'Pug', owner: 'Anat'}
    ]
    will return ['Izzi', 'Anat']
    */

`reduce` has nothing to do with what you want to achieve, anyway — Federico klez Culloca, May 14 '19 at 12:40
Uh, the edit removes rather useful information. Right now the question is super unclear about what the data and the requirement is. — VLAZ, May 14 '19 at 12:56
@FedericoklezCulloca to be fair, `reduce` can do it and it should be more performant than chaining `.filter` and `.map`. The latter are simpler to read to an extent but each will iterate the entire array *and* create a new array. A `reduce` is a common way to avoid the extra overhead of the eager evaluation in JS if you combine all the different operations in a `reduce`. — VLAZ, May 14 '19 at 13:05
@FedericoklezCulloca you can look into [transducers](https://medium.com/javascript-scene/transducers-efficient-data-processing-pipelines-in-javascript-7985330fe73d) if you are interested - in basic terms, they allow you to take a bunch of callbacks you would normally give to `filter`, `map`, and similar, but instead combine and run them with a single `reduce` operation. [And here is my favourite SO post about transducers](https://stackoverflow.com/questions/44198833/how-to-chain-map-and-filter-functions-in-the-correct-order/44211131#44211131) — VLAZ, May 14 '19 at 13:26

score 2 · Answer 1 · answered May 14 '19 at 12:42

let dogs = [ 
{name: 'Beatrice', breed: 'Lurcher', owner: 'Tom'}, 
{name: 'Max', breed: 'Pug', owner: 'Izzi'}, 
{name: 'Poppy', breed: 'Pug', owner: 'Anat'} ];

function getPugOwners(dogs) { 
  return dogs.filter(dog => dog.breed=='Pug').map(dog => dog.owner);
}

console.log(getPugOwners(dogs));

score 1 · Answer 2 · answered May 14 '19 at 12:40

1

you need to use 'map' method of Array

dogs.map(dog => dog.owner)

answered May 14 '19 at 12:40

marsibarsi

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1

Doesn't answer the question since OP only want Pug owners – PopHip May 14 '19 at 12:45
@PopHip ironically, with the current edit, this answer is correct, as there is no longer that requirement. – VLAZ May 14 '19 at 12:56

score 0 · Answer 3 · answered May 14 '19 at 12:47

you can create function like this:

let dogs = [ 
{name: 'Beatrice', breed: 'Lurcher', owner: 'Tom'}, 
{name: 'Max', breed: 'Pug', owner: 'Izzi'}, 
{name: 'Poppy', breed: 'Pug', owner: 'Anat'} ];


function getOwnerByBreed(dogs,breed) { 
  return dogs.filter(dog => dog.breed==breed).map(dog => dog.owner);
}


console.log('Pug Owners',getOwnerByBreed(dogs,'Pug'));

console.log('Lurcher Owners',getOwnerByBreed(dogs,'Lurcher'));

Return an array of names

3 Answers3