wp-ajax-example.js

(function($) {
  
  $.ajax({
    url: ajaxurl,
    action: 'my_wp_ajax_action'
  })
  .success(function(response) {
    if (typeof response.success === 'undefined') {
      // undefined error
    } else if (response.success === false) {
      // error (sent with wp_send_json_error)
    } else if (response.success === true ) {
      // success (sent with wp_send_json_success)
    } else {
      // something weird has happened
    }
  })
  .fail(function() {
    // network issues / no response etc.
  })
  .always(function() {
    // always do this, whether the request was successful or not
  });
  
})(jQuery);