I have the following JS class. I'm basically wrapping Websocket object inside a class

    class MyClass {
        
        // Main constructor
        constructor() {
            this.ws = null;
            this.ConnectionState = false;
        }   

        // Heart beat function
        #heartbeat() {
            // Do some stuff
        }

        // Initialization of the websocket
        Init() {                                    
            this.ws = new WebSocket("some url..."   );

            this.ws.onopen = function (event) {         
                this.ConnectionState = true;            
                this.#heartbeat();  // << The error is raised here
            }       
        }
    }

When running the method Init() , I'm getting the error : Uncaught TypeError: Object must be an instance of class MyClass at WebSocket.Init.ws.onopen

This happens in the row : this.#heartbeat();

Can anyone help with that please ?

Thanks