Javascript - filtering array with multiple same properties

afanoffriedrice
June 26, 2023
208 views
4 votes
5 Answers

so I have an array of values like this

const foodsList = [
  {
    foodOrigin: "Padang",
    foodCode: "SPI",
    foodName: "Nasi Padang"
  },
  {
    foodOrigin: "Padang",
    foodName: "Gulai",
    originCode: "PDN"
  },
  {
    foodOrigin: "Padang",
    foodName: "Rendang",
    originCode: "PDN"
  },
  {
    foodOrigin: "Palembang",
    foodName: "Pempek",
    originCode: "PLG"
  },
  {
    foodOrigin: "Palembang",
    foodName: "Tekwan",
    originCode: "PLG"
  },
  {
    foodOrigin: "Yogyakarta",
    foodName: "Gudeg",
    originCode: "YKT"
  }
];

and I want to filter the array so the result would be like this instead

const filteredFoodsList = [
  {
    foodOrigin: "Padang",
    originCode: "PDN"
  },
  {
    foodOrigin: "Palembang",
    originCode: "PLG"
  },
  {
    foodOrigin: "Yogyakarta",
    originCode: "YKT"
  }
];

In order to achieve the result, I tried doing it like below but is there a cleaner and better way to do this? ( especially since my actual array’s data consist of more than 500 )

const filteredFoodsList = [];
for (let i = 0; i < foodsList.length; i++) {
  if (i === 0) {
    filteredFoodsList.push({
      originCode: foodsList[i].originCode,
      foodOrigin: foodsList[i].foodOrigin
    });
  }
  let isExist = false;
  for (let j = 0; j < filteredFoodsList.length; j++) {
    if (foodsList[i].originCode === filteredFoodsList[j].originCode) {
      isExist = true;
    }
  }
  if (!isExist) {
    filteredFoodsList.push({
      originCode: foodsList[i].originCode,
      foodOrigin: foodsList[i].foodOrigin
    });
  }
}

Answers

As the OP stated there should be some focus on performance, so..

The Map could be the fastest way to collect unique values.
(I’ve borrowed Array.from(map, ([originCode, foodOrigin]) => ({ foodOrigin, originCode })) from Nina’s answer, really ellegant).

But it doesn’t affect the performance since the resulting array should be quite small.

But she forgot to include a Map::has() check that really improves the performance significantly.

What’s important how fast the source array is iterated. As always I see there can’t be a faster thing then for(let i = 0; ...)…

const foodsList=[{foodOrigin:"Padang",foodName:"Gulai",originCode:"PDN"},{foodOrigin:"Padang",foodName:"Rendang",originCode:"PDN"},{foodOrigin:"Palembang",foodName:"Pempek",originCode:"PLG"},{foodOrigin:"Palembang",foodName:"Tekwan",originCode:"PLG"},{foodOrigin:"Yogyakarta",foodName:"Gudeg",originCode:"YKT"}];

const map = new Map;
for (let i = 0; i < foodsList.length; i++) {
    const item = foodsList[i];
    map.has(item.originCode) || map.set(item.originCode, item.foodOrigin);
}

const result = Array.from(map, ([originCode, foodOrigin]) => ({ foodOrigin, originCode }));

console.log(result);

And a benchmark:

<script benchmark data-count="1">

    const chunk = [{ foodOrigin: "Padang", foodName: "Gulai", originCode: "PDN" }, { foodOrigin: "Padang", foodName: "Rendang", originCode: "PDN" }, { foodOrigin: "Palembang", foodName: "Pempek", originCode: "PLG" }, { foodOrigin: "Palembang", foodName: "Tekwan", originCode: "PLG" }, { foodOrigin: "Yogyakarta", foodName: "Gudeg", originCode: "YKT" }];
    var foodsList = [];
    let count = 10000000;
    while (count--) {
        foodsList.push(...chunk);
    }

    // @benchmark Nina's solution
    Array.from(
        foodsList.reduce((m, { foodOrigin, originCode }) => m.set(foodOrigin, originCode), new Map),
        ([foodOrigin, originCode]) => ({ foodOrigin, originCode })
    );

    // @benchmark Alexander's solution
    const map = new Map;
    for (let i = 0; i < foodsList.length; i++) {
        const item = foodsList[i];
        map.has(item.originCode) || map.set(item.originCode, item.foodOrigin);
    }

    Array.from(map, ([originCode, foodOrigin]) => ({ foodOrigin, originCode }));

    // @benchmark Nina's improved

    Array.from(
        foodsList.reduce((m, { foodOrigin, originCode }) => {
            m.has(foodOrigin) || m.set(foodOrigin, originCode);
            return m;
        }, new Map),
        ([foodOrigin, originCode]) => ({ foodOrigin, originCode })
    );


</script>
<script src="https://cdn.jsdelivr.net/gh/silentmantra/benchmark/loader.js"></script>

You can use an object to store the values

const foodsList = [{
  foodOrigin: 'Padang',
  foodCode: 'SPI',
  foodName: 'Nasi Padang',
}, {
  foodOrigin: 'Padang',
  foodName: 'Gulai',
  originCode: 'PDN',
}, {
  foodOrigin: 'Padang',
  foodName: 'Rendang',
  originCode: 'PDN',
}, {
  foodOrigin: 'Palembang',
  foodName: 'Pempek',
  originCode: 'PLG',
}, {
  foodOrigin: 'Palembang',
  foodName: 'Tekwan',
  originCode: 'PLG',
}, {
  foodOrigin: 'Yogyakarta',
  foodName: 'Gudeg',
  originCode: 'YKT',
}]

const items = {}

for (const item of foodsList) {
  if (item.originCode && !(item.originCode in items)) {
    items[item.originCode] = item
  }
}

const result = Object.values(items).map(({ originCode, foodName }) => ({ originCode, foodName }))

console.log(result)

You could take a Map and get a new array from it.

const
    foodsList = [{ foodOrigin: 'Padang', foodName: 'Gulai', originCode: 'PDN' }, { foodOrigin: 'Padang', foodName: 'Rendang', originCode: 'PDN' }, { foodOrigin: 'Palembang', foodName: 'Pempek', originCode: 'PLG' }, { foodOrigin: 'Palembang', foodName: 'Tekwan', originCode: 'PLG' }, { foodOrigin: 'Yogyakarta', foodName: 'Gudeg', originCode: 'YKT' }],
    result = Array.from(
        foodsList.reduce((m, { foodOrigin, originCode }) => m.set(foodOrigin, originCode), new Map),
        ([foodOrigin, originCode]) => ({ foodOrigin, originCode })
    );

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Here’s my "old-fashioned" approach without Map usage:

const foodsList = [ { foodOrigin: "Padang", foodCode: "SPI", foodName: "Nasi Padang" }, { foodOrigin: "Padang", foodName: "Gulai", originCode: "PDN" }, { foodOrigin: "Padang", foodName: "Rendang", originCode: "PDN" }, { foodOrigin: "Palembang", foodName: "Pempek", originCode: "PLG" }, { foodOrigin: "Palembang", foodName: "Tekwan", originCode: "PLG" }, { foodOrigin: "Yogyakarta", foodName: "Gudeg", originCode: "YKT" }];

const filteredFoodsList = foodsList.reduce(
  (acc, curr) =>
    curr.originCode &&
    !acc.some(a => a?.originCode === curr.originCode)
      ? [...acc, curr]
      : acc,
  []
);

console.log(filteredFoodsList);

+ + + explanation in progress + + +

const foodsList = [{
  foodOrigin: "Padang", foodCode: "SPI", foodName: "Nasi Padang"
  // and not ...
  // // foodOrigin: "Padang", foodName: "Nasi Padang", originCode: "SPI",
}, {
  foodOrigin: "Padang", foodName: "Gulai", originCode: "PDN",
}, {
  foodOrigin: "Padang", foodName: "Rendang", originCode: "PDN",
}, {
  foodOrigin: "Palembang", foodName: "Pempek", originCode: "PLG",
}, {
  foodOrigin: "Palembang", foodName: "Tekwan", originCode: "PLG",
}, {
  foodOrigin: "Yogyakarta", foodName: "Gudeg", originCode: "YKT",
}];


const { result } = foodsList
  .reduce(({ lookup, result }, { foodOrigin, originCode = null }) => {

    if (originCode !== null && !lookup.has(foodOrigin)) {

      lookup.set(foodOrigin, true);
      result.push({
        foodOrigin,
        originCode,
      });
    }
    return { lookup, result };

  }, { lookup: new Map, result: [] });

console.log({ result });

.as-console-wrapper { min-height: 100%!important; top: 0; }

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Javascript – filtering array with multiple same properties

Answers