1class Observable {
2  constructor(subscriber) {
3    this.subscriber = subscriber;
4  }
5
6  subscribe(observer) {
7    return this.subscriber(observer);
8  }
9
10  // Missing implementation
11  pipe(...operators) {
12    ____________________
13    ____________________
14    ____________________
15    ____________________
16  }
17}
18
19// Example operators
20const map = (fn) => (source) => 
21  new Observable(observer => 
22    source.subscribe({
23      next: (value) => observer.next(fn(value)),
24      error: (err) => observer.error(err),
25      complete: () => observer.complete()
26    })
27  );
28
29const filter = (predicate) => (source) => 
30  new Observable(observer =>
31    source.subscribe({
32      next: (value) => predicate(value) && observer.next(value),
33      error: (err) => observer.error(err),
34      complete: () => observer.complete()
35    })
36  );
37
38// Usage:
39const source$ = new Observable(observer => {
40  observer.next(1);
41  observer.next(2);
42  observer.next(3);
43  observer.complete();
44});
45
46const result$ = source$.pipe(
47  filter(x => x > 1),
48  map(x => x * 10)
49);