Adding delegates events handlers to button click

There can be different ways to add a handler to an event, or to set the only handler.

First, some background:

This is the simplest way, when you just set a handler:

someElement =
   document.getElementById("someId"); // I'm not going to check up your selectors 
                                      // without seeing your HTML and the specs
someElement.onclick =
   function(event) {/* ... */} // you can use event object
// or
someElement.onclick = function() {/* ... */}

You can add event handler (called event listener) and have more than one handler on the same element (same event instance):

someElement.addEventListener("click", function() {/* do something  */});

See: https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener[^].

Now, you might better understand what jQuery does: https://api.jquery.com/on.

That is,

someElement.on( "click", function() {
    // do something
});

In this function, the arguments selector and data are optional, please see the jQuery documentation page on "on" referenced above.

—SA