perftest.ts

// SETUP
function generateData(n) {
  const ids = new Array(n).fill(0).map((_, i) => i);
  return {
    notebooks: ids.map((x) => ({ id: x })),
    prices: ids
      .map((x) => [
        {
          entityId: x,
          price: 100,
          timestamp: new Date(),
        },
        {
          entityId: x,
          price: 200,
          timestamp: new Date(),
        },
        {
          entityId: x,
          price: 300,
          timestamp: new Date(),
        },
      ])
      .flat(),
  };
}

function getNotebooksWithPriceNaive(notes, prices) {
  return notes.map((notebook) => ({
    ...notebook,
    price: prices.filter((x) => x.entityId === notebook.id),
  }));
}

function getNotebooksWithPriceMap(notes, prices) {
  const pricesMap = prices.reduce((acc, price) => {
    if (acc.has(price.entityId)) {
      acc.get(price.entityId)?.push(price);
    } else {
      acc.set(price.entityId, [price]);
    }

    return acc;
  }, new Map());

  return notes.map((notebook) => ({
    ...notebook,
    prices: pricesMap.get(notebook.id),
  }));
}

const { notebooks, prices } = generateData(300);


// TEST1 - NAIVE
const res1 = getNotebooksWithPriceNaive(notebooks, prices);

// TEST2 - MAP
const res2 = getNotebooksWithPriceMap(notebooks, prices);

console.log(res1);
console.log(res2);