ui5 framework extend functionextend is actually returning a

extend is actually returning a new class by Metadata.createClass
create prototype chain
fnClass.prototype = jQuery.sap.newObject(fnBaseClass.prototype);
fnClass.prototype.constructor = fnClass;
Make the class visible as JS Object: jQuery.sap.setObject(sClassName, fnClass);
fnClass.getMetadata = fnClass.prototype.getMetadata = jQuery.sap.getter(oMetadata);