RxJs takeUntil and takeWhile

takeUntil in RxJava:

Observable<T> takeUntil(final Func1<? super T, Boolean> stopPredicate) {}

For example:

Observable.range(1, 10).takeUntil(i -> i > 5);

But takeUntil in RxJs:

.takeUntil(Observable); // It's connectable Observable not stopPredicate

Immediately, I just wrote takeWhile() for rx.js

rx.js:

  observableProto.takeWhile = function(whileFunc) {
      var source = this;
      return new AnonymousObservable(function(observer) {
        return source.subscribe(function(o) {
          if (whileFunc(o)) {
            observer.onNext(o);
          } else {     
            observer.onCompleted();
          }            
        }, function(e) {
          observer.onError(e);
        }, function() {
          observer.onCompleted();
        });            
      });              
  }; 

After, I found rx.js already has takeWhile(), sad..