ExtJS前台分页

Ext.onReady(function(){
				window.path = '<%=request.getContextPath()%>';
				Ext.QuickTips.init();
				Ext.BLANK_IMAGE_URL = path+'/jslib/ext2.2/resources/images/default/s.gif';
				init();
			});
			
			function getWidth(){
				return document.body.clientWidth;	
			}
			
			function getHeight(){
				return document.body.clientHeight;
			}
			
			function init(){
				new Ext.form.FieldSet({
					title:'查询区域',
					height: 'auto',
					contentEl:'query-form',
					collapsible:true,
					renderTo:'query-area',
					buttons:[
						{
							xtype:'button',
							text:'查询'
						},
						{
							xtype:'button',
							text:'重置',
							handler:function(){
								document.getElementById('query-form').reset();
							}
						}
					]
				});
				var fields = [
					{name:'a'},{name:'b'},{name:'c'},{name:'d'}
				];
				
				var datas = [];
				for(var i=0; i<100; i++){
					datas.push({a:'name151-'+(i+1),b:'area',c:2009,d:'description});
				}
				
				var proxy = new Ext.data.MemoryProxy({totalProperty:datas.length,root:[]});
				var store = new Ext.data.Store({
					remoteSort:false,
					reader:new Ext.data.JsonReader({
						totalProperty: 'totalProperty',
						root: 'root'
					},fields),
					proxy: proxy
				});
				store.on('beforeload', function(s, params){
					var start = params.params.start;
					var end = start + params.params.limit;
					//alert(start+", "+end +" Data's Size:"+datas.length);
					proxy.data = {totalProperty:datas.length,root:datas.slice(start, end)};
				});
				var fw = getWidth()-15;
				var gw = getWidth()-20;
				var fh = Math.round(getHeight()*0.6);
				new Ext.grid.GridPanel({
					title:'显示区域',
					width:fw,
					height:fh-20,
					collapsible:true,
					renderTo:'show-area',
					bbar: new Ext.PagingToolbar({
						store:store,
						pageSize:15
					}),
					store: store,
					columns:[
						new Ext.grid.RowNumberer(),
						{header:'A', align:'center', width:Math.round(gw*0.3), dataIndex:'a', sortable:true},
						{header:'B', align:'center', width:Math.round(gw*0.2), dataIndex:'b', sortable:true},
						{header:'C, align:'center', width:Math.round(gw*0.2), dataIndex:'c', sortable:true},
						{header:'D, align:'center', width:Math.round(gw*0.3), dataIndex:'d', sortable:true}
					],
					viewConfig: {
						forceFit: true
					},
					sm: new Ext.grid.RowSelectionModel({singleSelect:true})
				});
				store.load({params:{start:0,limit:15}});
			}