オブジェクトの配列から探す

const users = [
  { id: 1, name: '田中 太郎' },
  { id: 2, name: '佐藤 花子' },
];

console.log(users.find((user) => user.id === 2));
console.log(users.filter((user) => user.name.includes('田')));
console.log(users.some((user) => user.id === 1));

const users = [{ id: 1, name: '田中' }];

const user = users.find((u) => u.id === 99);

console.log(user?.name ?? '（見つかりません）');

const users = [{ email: 'TANAKA@example.com' }];
const keyword = 'tanaka';

console.log(
  users.filter((user) => user.email.toLowerCase().includes(keyword.toLowerCase())),
);

const decomposed = 'が';
const composed = 'が';

console.log(decomposed.length, composed.length);
console.log(decomposed === composed);
console.log([...decomposed].map((c) => c.codePointAt(0).toString(16)));
console.log(decomposed.normalize('NFC') === composed);

console.log('ﾀﾅｶ'.normalize('NFKC'));
console.log('ＡＢ'.normalize('NFKC'));

const normalize = (text) => text.normalize('NFKC').toLowerCase();

const users = [{ name: 'ﾀﾅｶ', email: 'TANAKA@example.com' }];
const keyword = normalize('たなか');

console.log(
  users
    .map((user) => ({ ...user, searchKey: normalize(user.name + user.email) }))
    .filter((user) => user.searchKey.includes(normalize('Tanaka'))),
);

const users = [
  { name: '田中', email: 'a@example.com', tel: '090' },
  { name: '佐藤', email: 'b@example.com', tel: '080' },
];

const keyword = '090';

console.log(
  users.filter((user) =>
    ['name', 'email', 'tel'].some((key) => String(user[key]).includes(keyword)),
  ),
);

const users = [
  { name: '田中', email: 'a@example.com' },
  { name: '佐藤', email: 'b@example.com' },
];

console.log(
  users.filter((user) => Object.values(user).some((value) => String(value).includes('佐'))),
);

const users = [
  { id: 1, name: 'a' },
  { id: 2, name: 'b' },
];

const byId = new Map(users.map((user) => [user.id, user]));

console.log(byId.get(2));
console.log(byId.get(99));