for KWhat_Work

Ext.onReady(function() {
  //The panel we'll be adding our nav items to
  var navGroup = new Ext.Panel({
    region: 'west',
    width:  180
  });
  
  //assuming this returns some JSON like {response: [{title: 'My Nav Item', html: 'some text'}, {title: 'Another item', html: 'test'}]}
  var store = new Ext.data.JsonStore({
      url:    '<?= RELATIVE_PATH ?>/Nav/View',
      root:   'response',
      fields: ['id', 'name']
  });
  
  store.load({
    
    //this gets called as soon as the store has finished loading
    callback: function(records) {
      //create a panel for each record, add each to navGroup
      Ext.each(records, function(record) {
        navGroup.add(new Ext.Panel(record));
      }, this);
      
      //force navGroup to make sure its child panels are rendered properly
      navGroup.doLayout();
    }
  });
  
  var viewport = new Ext.Viewport({
    layout: 'border',
    items: [
      ... your other panels, one of which must have "region: 'center'",
      navGroup
    ]
  });

  
});