A queue implemented in RxJS that will stream while subscribed and back up while no observers.

queue.ts

class Queue extends Subject<any> {
  private items;

  add(item) {
    if(this.observers.length > 0) {
      this.next(item);
    } else {
      this.items.push(item);
    }
  }

  subscribe(observer) {
    let s = super.subscribe(observer);
    this.items.forEach(item => this.next(item));
    this.items = [];
    return s;
  }
}