Hi,

In .xml

<button name="my_button" type="object" string="My Button" on_click="my_js_function"/>

js:-

function my_js_function() {
    // code for your JavaScript function goes here
  }
  // add event handler for button click event
  document.getElementById('my_button').addEventListener('click', function(event) {
    // call JavaScript function
    my_js_function();
    // prevent default action of button
    event.preventDefault();
  });

Regards