[JS] The Complete JavaScript Course 2021: From Zero to Expert! | # 165

Test Data

const dogs = [
  { weight: 22, curFood: 250, owners: ['Alice', 'Bob'] }, 
  { weight: 8, curFood: 200, owners: ['Matilda'] },
  { weight: 13, curFood: 275, owners: ['Sarah', 'John'] }, 
  { weight: 32, curFood: 340, owners: ['Michael'] },
];

 

Your tasks:

1. Loop over the 'dogs' array containing dog objects, and for each dog, calculate the recommended food portion and add it to the object as a new property. Do not create a new array, simply loop over the array. Forumla: recommendedFood = weight ** 0.75 * 28. (The result is in grams of food, and the weight needs to be in kg) -> task 1로 각  object에 'recFood' 추가

 

3 .Create an array containing all owners of dogs who eat too much ('ownersEatTooMuch') and an array with all owners of dogs who eat too little ('ownersEatTooLittle').

 

 

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callback Function 작성할 때마다 어떤 것을 parameter로 써야하는 지 감을 못 잡고, 혼자서 끙끙 앓았던 문제.

 

간단하게 하나씩 풀어갈 생각을 하면 되었는데도 Array.reduce()를 쓸 수 있을지 않을까 코드 작성해보다가 결국 막히고 해설영상을 보았더니 filter와 flatMap으로 작성하시더라... dogs가 Array로 구성 되어있어서 dog를 parameter로 넘겨주면 해결되는 매직-!

const ownersEatTooMuch = dogs
  .filter(dog => dog.curFood > dog.recFood)
  .flatMap(dog => dogs.owners);
    
const ownersEatTooLittle = dogs
  .filter(dog => dog.curFood < dog.recFood)
  .flatMap(dog => dogs.owners);
  
console.log(ownersEatTooMuch, ownersEatTooLittle);

일단은 'dogs'를 조건에 맞게 나누고 그 안에서 'owners'를 찾아 각각 하나의 Array로 만들어주기.

chain으로 엮어져 있기 때문에 어느 method를 먼저 사용할지도 고려해야한다.