求教，qml调用js报错

[lovelyIand]

import QtQuick 2.0
import QtQuick.Controls 1.1
import QtQuick.Window 2.0
import Qt.labs.settings 1.0
import "../controller/app.js" as Js

用qtcreator创建的qml项目，调用app.js文件时候报错，global变量不识别。求教大神
引用过程中报错，
qrc:/controller/app.js:2: ReferenceError: global is not defined