ez signals in ts

signals.ts

let activeEffect: (() => void) | null = null;

export function signal<T>(initialValue: T) {
  let value = initialValue;
  const subscribers = new Set<() => void>();

  return {
    get(): T {
      if (activeEffect) {
        subscribers.add(activeEffect);
      }
      return value;
    },
    set(newValue: T): void {
      if (value === newValue) return;
      value = newValue;
      subscribers.forEach((subscriber) => subscriber());
    },
  };
}

export function effect(fn: () => void) {
  const execute = () => {
    const prevEffect = activeEffect;
    activeEffect = execute;
    try {
      fn();
    } finally {
      activeEffect = prevEffect;
    }
  };

  execute();
}

export function computed<T>(fn: () => T) {
  const result = signal<T>(fn());
  effect(() => result.set(fn()));
  return result;
}


const count = signal(0);
const doubled = computed(() => count.get() * 2);

effect(() => {
  console.log("Count:", count.get());
  console.log("Doubled:", doubled.get());
});

count.set(5);

export type Signal<T> = ReturnType<typeof signal<T>>;