easy subscribe Stroe

store.ts

class Store<T> {
  private initialValue: T;
  private subscribers: ((nextValue: T)=> void)[] = [];

  constructor(initialValue?: T) {
    this.initialValue = initialValue;
  }

  set(nextValue: T) {
    this.initialValue = nextValue;
    this.subscribers.forEach((sub) => sub(nextValue));
  }
  
  get(): T {
    return this.initialValue;
  }
  
  /** value가 변경된 경우 callback의 해당 값을 보내줌 */
  watch(callback: (nextValue: T) => void){
    this.subscribers.push(callback);
    
    const index = this.subscribers.length -1;
    return {unWatch : this.unWatch.bind(this, index)};
  }

  private unWatch(index: number) {
    
    this.subscribers.splice(index, 1);
  }
}