src/jquery.nstSlider.js
function(isLeftGrip) {
            var $this = this,
                current_min_value = methods.get_current_min_value.call($this),
                current_max_value = methods.get_current_max_value.call($this),
                didValuesChange = false;

            // check if we changed.
            if (($this.data('beforestart_min') !== current_min_value) || 
                ($this.data('beforestart_max') !== current_max_value)
            ) {
                // values have changed!
                didValuesChange = true;

                // save the new values
                $this.data('beforestart_min', current_min_value);
                $this.data('beforestart_max', current_max_value);
            }


            var settings = $this.data('settings');

            settings.user_mouseup_callback.call($this, 
                methods.get_current_min_value.call($this),
                methods.get_current_max_value.call($this),
                isLeftGrip,
                didValuesChange
            );

            return $this;
        }
function(isLeftGrip) {
            var $this = this,
                current_min_value = methods.get_current_min_value.call($this),
                current_max_value = methods.get_current_max_value.call($this),
                didValuesChange = false;

            // check if we changed.
            if (($this.data('beforestart_min') !== current_min_value) || 
                ($this.data('beforestart_max') !== current_max_value)
            ) {
                // values have changed!
                didValuesChange = true;

                // save the new values
                $this.data('beforestart_min', current_min_value);
                $this.data('beforestart_max', current_max_value);
            }


            var settings = $this.data('settings');

            settings.user_mouseup_callback.call($this, 
                methods.get_current_min_value.call($this),
                methods.get_current_max_value.call($this),
                isLeftGrip,
                didValuesChange
            );

            return $this;
        }
/*
Calls the user mouseup callback with the right parameters. Relies on
$data('beforestart_min/max') in addition to the isLeftGrip parameter.

NOTE: saves the new beforestart_min and begforestart_max as well.