Uncaught TypeError: $.ajax is not a function when trying to use gon.watch in cytoscape

Question

This is my code. It's part the configuration of a library for context menus, and get's triggered if I click on an item in the context menu. Then I see the error mentioned in the title.

{
  [...]
  onClickFunction: function (event){
    [...]
    gon.watch("nodes", {}, function(){})
  }
},