Calling the JavaScript method greet(name) from Java works OK.
But when debugging my JavaScript code which should call the Java method this.$server.testCallBack();, $server is undefined.
Using Vaadin 19.
I think some things have changed here between Vaadin versions as some of the documentation refers to this.$server and others to element.$server.
From the documentation:
It marks a method in a Component subclass that can be called from the client side using the element.$server.serverMethodName(args) notation. In client-side Polymer template code, this refers to the corresponding element so that the calling convention is this.$server.serverMethodName(args).