extjs中的form表单提交bug

Ext.override(Ext.form.Action.Submit, {
                            processResponse: function(response){
                                this.response = response;
                                //增加下面几句代码就OK啦
                                ////////////////////////
                                var data = response.responseText;
                                if (data.indexOf('<pre') != -1 || data.indexOf('<PRE') != -1) {
                                    response.responseText = data.substring(data.indexOf('{'), data.length - 6);
                                    this.response = Ext.JSON.decode(response.responseText);
                                }
                                ///////////////////////////     
                                if (!response.responseText) {
                                    return true;
                                }
                                this.result = this.handleResponse(response);
                                return this.result;
                            }
                        });
=========================华丽分割线===================================
这样好像不太好使啊,如果pre标签中有值呢?
这样
Ext.override(Ext.form.Action.Submit, {
                            processResponse: function(response){
                                this.response = response;
                                //增加下面几句代码就OK啦
                                ////////////////////////
                                var data = response.responseText;
                                if (data.indexOf('<pre') != -1 || data.indexOf('<PRE') != -1) {
                                    response.responseText = data.substring(data.indexOf('{'), data.lastIndexOf('}')+1);
                                    this.response = Ext.JSON.decode(response.responseText);
                                }
                                ///////////////////////////     
                                if (!response.responseText) {
                                    return true;
                                }
                                this.result = this.handleResponse(response);
                                return this.result;
                            }
                        });