// 使用Object.freeze实现浅不可变
const immutableObj = Object.freeze({ count: 0 });

// 更新时创建新对象
const newObj = { ...immutableObj, count: immutableObj.count + 1 };

-- Haskell中使用Data.Map
import qualified Data.Map as Map

let m1 = Map.fromList [("a",1), ("b",2)]
let m2 = Map.insert "c" 3 m1  -- 创建新map而非修改原map

// Scala中使用State Monad
case class State[S, A](run: S => (A, S)) {
  def flatMap[B](f: A => State[S, B]): State[S, B] = 
    State(s => {
      val (a, s1) = run(s)
      f(a).run(s1)
    })
}

// 使用IO Monad隔离副作用
class IO<A> {
  constructor(public unsafePerformIO: () => A) {}
  static of<B>(b: B): IO<B> {
    return new IO(() => b);
  }
  map<B>(f: (a: A) => B): IO<B> {
    return new IO(() => f(this.unsafePerformIO()));
  }
}