Replace link with form to pass variables to javascript / ajax

Worked out the answer with input from non WP-oriented forum and edited above to show.

In short the variables were retrieved from WITHIN the js function using getElementByID and prevented error on non-action form with event.preventDefault();

like so:

function glitch_player_display() {
        user_input = document.getElementById("user_input").value ? document.getElementById("user_input").value : 2;
        generated_var = document.getElementById("generated_var").value ? document.getElementById("generated_var").value : "Default_Var";
        $(document).on('submit', '#form_id', function(event){
            event.preventDefault();
        });//etc...