Abstract: Systems and methods are provided for generating event handlers on-the-fly in a JavaScript Object Notation (JSON) environment. One embodiment is a system that includes a memory storing multiple JSON files. Each JSON file stores JSON objects that each define controls of a Graphical User Interface (GUI). The system also includes a controller that loads a primary JSON file from the memory, generates a GUI including controls defined by the primary JSON file, transmits instructions to a display to present the GUI to a user, and detects input from a user interface indicating user interaction with one of the controls. In response to the input, the controller loads a JSON extension file defining additional controls for the GUI, populates the GUI with the additional controls, analyzes the JSON extension file to determine event handlers defined for the additional controls, and sets up the event handlers for the additional controls.