Extjs의 checkbox 전체 선택 및 반선택

Ext.create('Ext.form.Panel', {
	    title: 'Checkbox Group',
	    width: 300,
	    height: 125,
	    bodyPadding: 10,
	    renderTo: Ext.getBody(),
	    items:[{
	        xtype: 'checkboxgroup',
	        fieldLabel: 'Two Columns',
	        id:'cg',
	        // Arrange radio buttons into two columns, distributed vertically
	        columns: 2,
	        vertical: true,
	        items: [
	            { boxLabel: 'Item 1', name: 'rb', inputValue: '1' },
	            { boxLabel: 'Item 2', name: 'rb', inputValue: '2', checked: true },
	            { boxLabel: 'Item 3', name: 'rb', inputValue: '3' },
	            { boxLabel: 'Item 4', name: 'rb', inputValue: '4' },
	            { boxLabel: 'Item 5', name: 'rb', inputValue: '5' },
	            { boxLabel: 'Item 6', name: 'rb', inputValue: '6' }
	        ]
	    }]
	    ,bbar: [
		        {
		            text: ' ',
		            handler: function() {
		        		var array = Ext.getCmp('cg').items;
		        		array.each(function(item){
//		        			alert(item.getValue());
		        			if(item.getValue()==true){
		        				item.setValue(false);
		        			}else{
		        				item.setValue(true);
		        			}
		        		});
//		        		alert(Ext.getCmp('cg').items.length);
		            }
		        },
		        '-',
		        {
		            text: ' ',
		            handler: function() {
			        	var array = Ext.getCmp('cg').items;
		        		array.each(function(item){
		        		    item.setValue(true);
		        		});
		            }
		        } 
		    ]
	});