QML string type accessed from JS files to be undefined unexpectedly when running on ARM.

QML Item type has properties of state and objectName, which are string type.
// MyItem.qml
Item {
id: root
objectName: "hello item"
...
}
Using root.objectName and root.state to output some logs in JS files, it's good on PC.
But on ARM, the log is undefined of root.objectName and root.state and
other types is ok except for the string type.