Pausable Observable that accumulates values. Run at https://observable-playground.github.io/gist/1d6bb94e2122d75fbbc51a52aafa50c7

_.txt

creates a stream that will not emit values until trigger$ emits.
then all events from the source$ are emited at once and continue
emiting on a normal schedule

source$      --0--1---2--------3--4--
trigger$     -----------o------------

                        0
result$      -----------1-----3--4---
                        2

RX_hold.js

const { rxObserver } = require('api/v0.3');
const { Observable, Subject, BehaviorSubject } = require('rxjs/Rx');


const trigger$ = Observable.of('o').delay(10);
const source$ = Observable.interval(3).take(5);
const afterTrigger$ = source$.skipUntil(trigger$);

const result$ = 
  source$
  .buffer(trigger$)
  .take(1)
  .switchMap(x=>Observable.from(x))
  .merge(afterTrigger$);


source$.subscribe(rxObserver('source$'));
trigger$.subscribe(rxObserver('trigger$'));
result$.subscribe(rxObserver('result$'));