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

In my case, I was unable to predict what the final value would be. I also just wanted a solution involving common, easy operators, and I wanted something I could reuse, so I couldn't rely on the values being truthy. The only thing I could think of was defining my own operator like this:

import { pipe, from } from 'rxjs';
import { switchMap, takeWhile, filter, map } from 'rxjs/operators';

export function doWhile(shouldContinue: (a: T) => boolean) {
  return pipe(
    switchMap((data: T) => from([
      { data, continue: true },
      { data, continue: shouldContinue(data), exclude: true }
    ])),
    takeWhile(message => message.continue),
    filter(message => !message.exclude),
    map(message => message.data)
  );
}

It's a little weird, but it works for me and I can import it and use it.