heroes.ts

const COUNT = 10000;

interface Hero {
  heroName: string;
  heroId: number;
}

interface AlterEgo {
  realName: string;
  heroId: number;
}

interface RevealedHero {
  heroName: string;
  realName: string;
}

const generateHeroArray = (): Hero[] =>
  Array(COUNT)
    .fill("")
    .map((heroName, heroId) => ({ heroName, heroId }));

const generateAlterEgoArray = (): AlterEgo[] =>
  Array(COUNT)
    .fill("")
    .map((realName, heroId) => ({ realName, heroId }));

const combine1 = (heroArr: Hero[], alterEgoArr: AlterEgo[]): RevealedHero[] =>
  heroArr.map(hero => {
    const alterEgo = alterEgoArr.find(x => x.heroId === hero.heroId);
    return {
      heroName: hero.heroName,
      realName: alterEgo!.realName
    };
  });

const combine2 = (
  heroArr: Hero[],
  alterEgoArr: AlterEgo[]
): { [heroId: number]: RevealedHero } =>
  heroArr.reduce(
    (acc, { heroId, heroName }) => ({
      ...acc,
      [heroId]: { ...acc[heroId], heroName }
    }),
    alterEgoArr.reduce(
      (acc, { heroId, realName }) => ({
        ...acc,
        [heroId]: { ...acc[heroId], realName }
      }),
      {} as { [heroId: number]: RevealedHero }
    )
  );

const combine3 = (heroes: Hero[], alterEgos: AlterEgo[]): RevealedHero[] => {
  const heroMap: { [heroId: number]: string } = heroes.reduce(
    (acc, { heroId, heroName }) => ({ ...acc, [heroId]: heroName }),
    {}
  );
  const alterEgoMap: { [heroId: number]: string } = alterEgos.reduce(
    (acc, { heroId, realName }) => ({ ...acc, [heroId]: realName }),
    {}
  );
  return heroes.map(({ heroId }) => ({
    heroName: heroMap[heroId],
    realName: alterEgoMap[heroId]
  }));
};

const combine4 = (heroes: Hero[], alterEgos: AlterEgo[]): RevealedHero[] => {
  const heroMap: { [heroId: number]: string } = {};
  heroes.forEach(({ heroId, heroName }) => (heroMap[heroId] = heroName));

  const alterEgoMap: { [heroId: number]: string } = {};
  alterEgos.forEach(({ heroId, realName }) => (alterEgoMap[heroId] = realName));

  return heroes.map(({ heroId }) => ({
    heroName: heroMap[heroId],
    realName: alterEgoMap[heroId]
  }));
};

const combine5 = (
  heroArr: Hero[],
  alterEgoArr: AlterEgo[]
): { [heroId: number]: RevealedHero } =>
  heroArr.reduce(
    (acc, { heroId, heroName }) => {
      acc[heroId].heroName = heroName;
      return acc;
    },
    alterEgoArr.reduce(
      (acc, { heroId, realName }) => {
        acc[heroId] = { realName } as RevealedHero;
        return acc;
      },
      {} as { [heroId: number]: RevealedHero }
    )
  );

const heroes = generateHeroArray();
const alterEgos = generateAlterEgoArray();

console.log(`At ${COUNT} items to combine:`);

console.time("combine1");
combine1(heroes, alterEgos);
console.timeEnd("combine1");

console.time("combine2");
combine2(heroes, alterEgos);
console.timeEnd("combine2");

console.time("combine3");
combine3(heroes, alterEgos);
console.timeEnd("combine3");

console.time("combine4");
combine4(heroes, alterEgos);
console.timeEnd("combine4");

console.time("combine5");
combine5(heroes, alterEgos);
console.timeEnd("combine5");