RxJS takeWhile but include the last value

Question

I have a RxJS5 pipeline looks like this

Rx.Observable.from([2, 3, 4, 5, 6])
  .takeWhile((v) => { v !== 4 })

I want to keep the subscrip

Answer 1

Since RxJS 6.4.0 this is now possible with takeWhile(predicate, true).

There's already an opened PR that adds an optional inclusive parameter to takeWhile: https://github.com/ReactiveX/rxjs/pull/4115

There're at least two possible workarounds:

1. using concatMap():

   of('red', 'blue', 'green', 'orange').pipe(
     concatMap(color => {
       if (color === 'green') {
         return of(color, null);
       }
       return of(color);
     }),
     takeWhile(color => color),
   )
   

2. Using multicast():

   of('red', 'blue', 'green', 'orange').pipe(
     multicast(
       () => new ReplaySubject(1),
       subject => subject.pipe(
         takeWhile((c) => c !== 'green'),
         concat(subject.take(1),
       )
     ),
   )
   

I've been using this operator as well so I made it to my own set of additional RxJS 5 operators: https://github.com/martinsik/rxjs-extra#takewhileinclusive

This operator has been also discussed in this RxJS 5 issue: https://github.com/ReactiveX/rxjs/issues/2420

Jan 2019: Updated for RxJS 6