왜

필터 -- 引数の条件での絞り込み。

動作

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => word.length > 6);

console.log(result);

프로다크트에서 使われそうな実例

const customers = [
  {
    id: 1,
    address: {
      number: "1-1-1" ,
      zipCode: "123-1111" ,
    } 
  },
  {
    id: 2,
    address: {
      number: "2-2-2",
      zipCode: "123-2222" ,
    } 
  },
]
const getElibgleCustomers = (customers, zipCode) => {
  return customers.filter(
    (customer) => customer.address.zipCode === zipCode
  );
}
const results = getElibgleCustomers(customers, "123-2222")

console.log(results);

// [ { id: 2, address: { number: '2-2-2', zipCode: '123-2222' } } ]

포함 -- 引数の値での絞り込み。

const numbers = [1, 2, 3, 4, 5];

const includesFive = numbers.includes(5);

줄이기 -- 引数の処理を Lisp 的に施す.

지도 -- 引数の関数を配列の要素ひとつひとつに施す.