Extjs, UI manipulation using parent element id and get its childs from class applied

That's what use this logic on store load , one the stored load success then manipulate you UI( use this on render function of under use controll):

 onGridRendered: function (grid) {
       store.load({
           scope: this,
           callback: function (records, operation, success) {
               if (success) {
                   var parent = Ext.get('ID of element');
                   var elems = parent.select("div.class of elements").elements;
                   for (var i = 0; i < elems.length; i++) {
                       elems[i].hidden = true;
                   }
               }

           }
       });
}