take.js

  var TakeObservable = (function(__super__) {
    inherits(TakeObservable, __super__);
    function TakeObservable(source, count) {
      this.source = source;
      this._count = count;
      __super__.call(this);
    }

    TakeObservable.prototype.subscribeCore = function (o) {
      return this.source.subscribe(new TakeObserver(o, this._count));
    };

    function TakeObserver(o, c) {
      this._o = o;
      this._c = c;
      this._r = c;
      AbstractObserver.call(this);
    }

    inherits(TakeObserver, AbstractObserver);

    TakeObserver.prototype.next = function (x) {
      if (this._r-- > 0) {
        this._o.onNext(x);
        this._r <= 0 && this._o.onCompleted();
      }
    };

    TakeObserver.prototype.error = function (e) { this._o.onError(e); };
    TakeObserver.prototype.completed = function () { this._o.onCompleted(); };

    return TakeObservable;
  }(ObservableBase));

  /**
   *  Returns a specified number of contiguous elements from the start of an observable sequence, using the specified scheduler for the edge case of take(0).
   * @param {Number} count The number of elements to return.
   * @param {Scheduler} [scheduler] Scheduler used to produce an OnCompleted message in case <paramref name="count count</paramref> is set to 0.
   * @returns {Observable} An observable sequence that contains the specified number of elements from the start of the input sequence.
   */
  observableProto.take = function (count, scheduler) {
    if (count < 0) { throw new ArgumentOutOfRangeError(); }
    if (count === 0) { return observableEmpty(scheduler); }
    return new TakeObservable(this, count);
  };