Custom json format javascript error

Custmer json format add {"status": "202", "code": "2001","data": {grape object json}}, But i get a javascript error.

module API
  module APIHelpers

    module JSendSuccessFormatter
      def self.call(object, env)
        { status: '200', code: '2001', data: object }.to_json
      end
    end

    module JSendErrorFormatter
      def self.call(message, backtrace, options, env)
        if message.is_a?(Hash)
          { :status => 'fail', :data => message }.to_json
        else
          { :status => 'error', :message => message }.to_json
        end
      end
    end

    module ExceptionHandlers
      def self.included(base)
        base.instance_eval do
          rescue_from Grape::Exceptions::ValidationErrors do |e|
            Rack::Response.new({
              error: { code: 1001, message: e.message }
            }.to_json, e.status)
          end
        end
      end
    end

  end
end

module API
  class API < Grape::API
    version 'v1'
    prefix 'api'
    format :json

    helpers APIHelpers

   formatter :json, APIHelpers::JSendSuccessFormatter
   error_formatter :json, APIHelpers::JSendErrorFormatter
......
.....

optput

{
  "status": "200",
  "code": "2001",
  "data": {
    "id": 1,
    "title": "title",
    "summary": "summary",
    "content": "content",
    "title_link": "title_link",
    "must_read": true,
    "slug": "slug",
    "state": "publish",
    "draft_key": "draft_key",
    "created_at": "2015-01-13T14:24:05.943+08:00",
    "updated_at": "2015-01-13T14:24:05.943+08:00",
    "cover": {
      "url": null
    }
  }
}

[Error] TypeError: undefined is not an object (evaluating 'response.apis.length')
    buildFrom1_1Spec (swagger-ef0b13e38d9e65fe2645c7219034874d.js, line 217)
    response (swagger-ef0b13e38d9e65fe2645c7219034874d.js, line 143)
    response (swagger-ef0b13e38d9e65fe2645c7219034874d.js, line 1479)
    emit (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 1391)
    emit (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 1191)
    (anonymous function) (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 1211)
    setBodyAndFinish (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 1815)
    (anonymous function) (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 1832)
    emit (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 1388)
    handle (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 2715)
    onreadystatechange (shred.bundle-945ecf92347d2bf3ab1b35dd24ed25cb.js, line 2584)

Start with APIHelpers::JSendSuccessFormatter and the API class's formatter configuration, then trace the response through buildFrom1_1Spec in swagger-ef0b13e38d9e65fe2645c7219034874d.js. Done means the shown custom JSON response no longer causes the response.apis.length error, with coverage for the reported payload.