Detect field change in ExtJS

gistfile1.js

var panel = new Ext.form.FormPanel({
		title: 'Example',
		width: 350,
		items: [],
		listeners: {
		    add: function(me, component, index) {
  		    component.on('change', function(f,n,o) {
  		        alert('detected! '+f.label+' value changed from '+o+' to '+n);
  		        console.log(component.startValue);
  		    });
		  }
	  }
});

gistfile2.js

// example on render or load
example.form.load({
				url: '/my/api',
				params: {id: 5},
				success: function(result, request) {

					var form = example.getForm();
				
					 form.items.each(function(field){
					 	field.on('change',function(f,n,o){
					 		alert('detected! '+f.label+' value changed from '+o+' to '+n);
					 	});
					 });

				}
			});