Filtering array to get array of objects in ES6

Question

How do I filter the array to get the result as an array of objects?

Here's what I was trying to do

const getCars = (cars, carNames) => {
  const result = carNames.map((carName) =>
    cars.filter(
      (car) =>
      car.name === carName
    )
  );
  console.log('result', result);
  return result;
};

const cars = [{
  name: 'BMW',
  type: '2020'
}, {
  name: 'Audi',
  type: '2019'
}, {
  name: 'Benz',
  type: '2018'
}]

getCars(cars, ['BMW', 'Benz']);

I'm expecting output to be an array of objects but what I'm getting is array of arrays. Could anyone please help?

[{name: 'BMW', type: '2020'},{name: 'Benz', type: '2018'}]

`filter` the `cars` array and check if the name is included in `carNames` like this:`cars.filter(c => carNames.includes(c.name))`. If the arrays are big, you could create a `const set = new Set(carNames)` and use `set.has(c.name)` inside the filter — adiga, Jun 29 '20 at 19:05

Unmitigated · Accepted Answer · 2020-06-29T19:08:25.060

You are getting an array of arrays because Array#map converts each element in an array to the return value of the function passed to it when called with the element. You are returning an array from the function each time, so each element is replaced with an array. Use Array#flatMap instead, which flattens the array after mapping.

const getCars = (cars, carNames) => {
  const result = carNames.flatMap((carName) =>
    cars.filter(
      (car) =>
      car.name === carName
    )
  );
  console.log('result', result);
  return result;
};

const cars = [{
  name: 'BMW',
  type: '2020'
}, {
  name: 'Audi',
  type: '2019'
}, {
  name: 'Benz',
  type: '2018'
}]

getCars(cars, ['BMW', 'Benz']);

For better efficiency, you can use Array#filter on the cars array and only keep the elements whose name is contained in the carNames array.

const getCars = (cars, carNames) => {
  const result = cars.filter(({name})=>carNames.includes(name));
  console.log('result', result);
  return result;
};

const cars = [{
  name: 'BMW',
  type: '2020'
}, {
  name: 'Audi',
  type: '2019'
}, {
  name: 'Benz',
  type: '2018'
}]

getCars(cars, ['BMW', 'Benz']);

score 1 · Answer 2 · answered Jun 29 '20 at 19:03

You can merge all the arrays into one by following statement:

const merged = [].concat.apply([], getCars(cars, ['BMW', 'Benz']));

Or you can update the getCars function with the same:

const getCars = (cars, carNames) => {
  const result = carNames.map((carName) =>
    cars.filter(
      (car) =>
      car.name === carName
    )
  );
  console.log('result', result);
  return [].concat.apply([], results);
};

Filtering array to get array of objects in ES6

2 Answers2