src/jquery.nstSlider.js
function () {
            var $this = this,
                settings = $this.data('settings');

                if ($this.data('has_right_grip')) {
                    return _methods.getGripPositionPx.call($this,
                        $this.find(settings.right_grip_selector)
                    );
                }

                // default
                var sliderWidthPx = _methods.getSliderWidthPx.call($this) - $this.data('left_grip_width');
                return _methods.rangemap_0_to_n.call($this, $this.data('cur_max'), sliderWidthPx);
         }
function () {
            var $this = this,
                settings = $this.data('settings');

                if ($this.data('has_right_grip')) {
                    return _methods.getGripPositionPx.call($this,
                        $this.find(settings.right_grip_selector)
                    );
                }

                // default
                var sliderWidthPx = _methods.getSliderWidthPx.call($this) - $this.data('left_grip_width');
                return _methods.rangemap_0_to_n.call($this, $this.data('cur_max'), sliderWidthPx);
         }
/*
Return the position of the right Grip if it exists or return the
current position if not. Even if the right grip doesn't exist, its
position should be defined, as it determines the position of the
bar.