在javascript函数中减少多个if语句

const age = 18;
const isAdult = age >= 18 ? true : false;
console.log(isAdult); // 输出: true

const age = 18;
const isAdult = age >= 18 && true || false;
console.log(isAdult); // 输出: true

const actions = {
  'login': () => console.log('登录'),
  'logout': () => console.log('登出'),
  'register': () => console.log('注册')
};

const action = 'login';
if (actions[action]) {
  actions[action]();
} else {
  console.log('未知操作');
}

const day = 'Monday';
switch (day) {
  case 'Monday':
    console.log('星期一');
    break;
  case 'Tuesday':
    console.log('星期二');
    break;
  default:
    console.log('其他星期');
}

const isAdult = age => age >= 18;
const isMinor = age => !isAdult(age);

const age = 18;
console.log(isAdult(age)); // 输出: true
console.log(isMinor(age)); // 输出: false