How to use the framebus.on function in framebus

handler = function () {
      /* eslint-disable no-invalid-this */
      if (checkOrigin(this.origin, self.merchantUrl)) {
        originalHandler.apply(this, arguments);
      }
      /* eslint-enable no-invalid-this */
    };
  }

  namespacedEvent = this._namespaceEvent(eventName);
  args = Array.prototype.slice.call(arguments);
  args[0] = namespacedEvent;
  args[1] = handler;

  this._log('on', args);
  bus.on.apply(bus, args);

  this._listeners.push({
    eventName: eventName,
    handler: handler,
    originalHandler: originalHandler
  });
};

it('proxies to Framebus\'s on', function () {
      this.bus.on(this.event, this.handler);
      expect(framebus.on).to.be.calledWith('braintree:foo:' + this.event, this.handler);
    });

it('doesn\'t proxy to framebus after calling', function () {
      this.bus.teardown();

      this.bus.on(this.event, this.handler);
      expect(framebus.on).not.to.be.called;

      this.bus.off(this.event, this.handler);
      expect(framebus.off).not.to.be.called;

      this.bus.emit(this.event);
      expect(framebus.emit).not.to.be.called;
    });
  });