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How to filter an array of objects storing only once for each matched item

I'm working with Javascript, and have the following array of objects:

const offersStep = [
     {a: 1, price: 67.10},
     {a: 3, price: 88.20},
     {a: 5, price: 88.20}, 
     {a: 7, price: 57.10},
     {a: 13, price: 57.10},
     {a: 15, price: 57.10},
     {a: 29, price: 57.10},
     {a: 30, price: 57.10},
]

What and How i have to do, in order to store in a new array, those objects, ignoring it those who the prop price has a value who is already stored on the new array?

Expected output:

offers = [
  {a: 1, price: 67.10},
  {a: 3, price: 88.20},
  {a: 7, price: 57.10}
]

3 months ago ·

Juan Pablo Isaza

3 answers

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Answer 1 · 2022-06-28T04:47:27.648Z

You can store the objects in a Map keyed off its price. After you have stored unique prices, spread the values() iterator of the Map into a new array to get your result.

const offersStep = [
     {a: 1, price: 67.10},
     {a: 3, price: 88.20},
     {a: 5, price: 88.20}, 
     {a: 7, price: 57.10},
     {a: 13, price: 57.10},
     {a: 15, price: 57.10},
     {a: 29, price: 57.10},
     {a: 30, price: 57.10},
];

function filterOffers(offers) {
  let offersByPrice = new Map();
  for (let offer of offers) {
    if (!offersByPrice.has(offer.price)) {
      // Store the offer
      offersByPrice.set(offer.price, offer);
    }
  }
  
  return [...offersByPrice.values()];
}

console.log(filterOffers(offersStep));

Answer 2 · 2022-06-28T04:47:27.657Z

Idea

Filter the original array, keeping tabs on the prices encountered so far by means of a set.

Code

const offersStep = [
     {a: 1, price: 67.10},
     {a: 3, price: 88.20},
     {a: 5, price: 88.20}, 
     {a: 7, price: 57.10},
     {a: 13, price: 57.10},
     {a: 15, price: 57.10},
     {a: 29, price: 57.10},
     {a: 30, price: 57.10}
];

let offer
  , nset_prices = new Set() 
  ;

offer = offersStep.filter ( po_item => {
            let b_ok = !nset_prices.has(po_item.price)
              ;

            if (b_ok) {
                nset_prices.add(po_item.price)
            }
            return b_ok;
        });

console.log(offer);

Answer 3 · 2022-06-28T04:47:27.664Z

Let me if the code works for you!

const offersStep = [
  { a: 1, price: 67.1 },
  { a: 3, price: 88.2 },
  { a: 5, price: 88.2 },
  { a: 7, price: 57.1 },
  { a: 13, price: 57.1 },
  { a: 15, price: 57.1 },
  { a: 29, price: 57.1 },
  { a: 30, price: 57.1 },
];

let tempOffers = {};

offersStep.forEach((eachObj) => {
  const { price } = eachObj;
  if (!tempOffers[price]) {
    tempOffers[price] = eachObj;
  }
});

const offers = Object.values(tempOffers);

console.log("offers are", offers);