The source code

    /*!
     * Ext JS Library 3.3.1
     * Copyright(c) 2006-2010 Sencha Inc.
     * licensing@sencha.com
     * http://www.sencha.com/license
     */
    /**
     * Plugin for PagingToolbar which replaces the textfield input with a slider
     */
    Ext.ux.SlidingPager = Ext.extend(Object, {
        init : function(pbar){
            var idx = pbar.items.indexOf(pbar.inputItem);
            Ext.each(pbar.items.getRange(idx - 2, idx + 2), function(c){
                c.hide();
            });
            var slider = new Ext.Slider({
                width: 114,
                minValue: 1,
                maxValue: 1,
                plugins: new Ext.slider.Tip({
                    getText : function(thumb) {
                        return String.format('Page {0} of {1}', thumb.value, thumb.slider.maxValue);
                    }
                }),
                listeners: {
                    changecomplete: function(s, v){
                        pbar.changePage(v);
                    }
                }
            });
            pbar.insert(idx + 1, slider);
            pbar.on({
                change: function(pb, data){
                    slider.setMaxValue(data.pages);
                    slider.setValue(data.activePage);
                }
            });
        }
    });