EXTJS 4 How to get Json response back on success of submit in form? -

i able see json response in firebug , when decode action of form on success giving undefined .

{     xtype: 'form',     x: 30,     y: 520,     height: 80,     bodypadding: 10,     title: 'myuploadform',     fileupload: true,     standardsubmit: false,     autoheight: true,     bodystyle: 'padding: 10px 10px 10px 10px;',     labelwidth: 50,      items:[{         xtype: 'fileuploadfield',         id: 'filedata',         emptytext: 'select document upload...',         fieldlabel: 'file',         buttontext: 'browse'     }],      buttons: [{         text: 'upload',         handler: function() {             var form = this.up('form').getform();             if(form.isvalid()){                 alert("submit");                  form.submit({                     url: 'myurl'                     waitmsg: 'uploading file...',                      success: function (form,action) {                         var data= ext.json.decode(action.response.responsetext);                         alert("success: " + data.msg);                         ext.msg.alert('success', action.result.message);                     },                      failure: function (form, action) {                         var data = ext.decode(action.response.responsetext);                         alert("failure: " + data.msg);                     }                 });             }         }     }] } 

my url returns json response want handle in success of submit . if tried pls let me know

try plain javascript way

var data= json.parse(action.response.responsetext); 

or extjs 3.x way

var data= ext.util.json.decode(action.response.responsetext); 

for extjs 4 , above

var data= ext.json.decode(action.response.responsetext);