tips

tips.md

オブジェクトの配列で重複した要素を削除する

const distinctArray = array => {
  const cleanList = array.filter((value1, index, array) => {
    // findIndex : 同じ要素があればそのインデックスを返す
    // nameの値が同じもののインデックスと全体のインデックスが同じものだけ抽出
    return array.findIndex(value2 => value1.name === value2.name) === index;
  });

  return cleanList;
};

const users = [
  { name: 'tkd1', age: 18 },
  { name: 'tkd2', age: 20 },
  { name: 'tkd3', age: 22 },
  { name: 'tkd2', age: 25 },
  { name: 'tkd3', age: 26 }
];

const distinctUsers = distinctArray(users);
console.log(distinctUsers); // [  { name: 'tkd1', age: 18 },{ name: 'tkd2', age: 20 },{ name: 'tkd3', age: 22 },]

時間でSort

const sortByTime = (array: any) => {
  return array.sort((a: any, b: any) => {
    if (a.time < b.time) return -1
    if (a.time > b.time) return 1
    return 0
  })
}

const fruits = [ { orange: 100, apple: 120 }, { orange: 120, apple: 180 }, { orange: 130, apple: 240 }, { orange: 140, apple: 120 }, { orange: 150, apple: 180 } ];

合計

const total = fruits.reduce((acc, currentValue) => {
  return acc + currentValue.orange;
}, 0);
console.log(total);

最大値 / 最小値

const users = [
  { name: 'tkd1', age: 18 },
  { name: 'tkd2', age: 20 },
  { name: 'tkd3', age: 22 },
  { name: 'tkd2', age: 25 },
  { name: 'tkd3', age: 26 }
];

// 最大
const maxAgeUser = users.reduce((acc, currentValue, index) =>
  acc.age > currentValue.age ? acc : currentValue
);
console.log(maxAgeUser);

// 最小値
const minAgeUser = users.reduce((acc, currentValue, index) =>
  acc.age < currentValue.age ? acc : currentValue
);
console.log(minAgeUser);