I'm writing a piece of HTML and JavaScript code, and I need to check if inputs have been filled before loading button after click on it. However, when I leave them blank, it proceeds to the PHP page passing the variables empty.

What I need is to add validation the forms to this code before loading button & disabled.

$(document).ready(function() {
  $("#btnFetch").click(function() {
    // disable button
    $(this).prop("disabled", true);
    // add spinner to button
    $(this).html(
      '<i class="fa fa-circle-o-notch fa-spin"></i> loading...'
    );
  });
});