Opaque comment
Since you have defined attribute “displayMode” as type Boolean, so it can be assigned with true of false.
Code robustness
Further study:
http://help.sap.com/saphelp_uiaddon10/helpdata/en/56/2803c6f55c49608d01a453cc0590ab/frameset.htmif we are in ui component context, we do not need to concatenate id prefix and id body manually, as suggested by sap help above:
Create all views, controls, and elements in a UI component by using the this.createId() method and retrieve them by using the this.byId() method.