jQuery event to trigger action when a div is made visible

There is no native event you can hook into for this however you can trigger an event from your script after you have made the div visible using the .trigger function

e.g

//declare event to run when div is visible
function isVisible(){
   //do something

}

//hookup the event
$('#someDivId').bind('isVisible', isVisible);

//show div and trigger custom event in callback when div is visible
$('#someDivId').show('slow', function(){
    $(this).trigger('isVisible');
});

The problem is being addressed by DOM mutation observers. They allow you to bind an observer (a function) to events of changing content, text or attributes of dom elements.

With the release of IE11, all major browsers support this feature, check http://caniuse.com/mutationobserver

The example code is a follows:

$(function() {
  $('#show').click(function() {
    $('#testdiv').show();
  });

  var observer = new MutationObserver(function(mutations) {
    alert('Attributes changed!');
  });
  var target = document.querySelector('#testdiv');
  observer.observe(target, {
    attributes: true
  });

});

<div id="testdiv" style="display:none;">hidden</div>
<button id="show">Show hidden div</button>

<script type="text/javascript" src="https://code.jquery.com/jquery-1.9.1.min.js"></script>

You could always add to the original .show() method so you don't have to trigger events every time you show something or if you need it to work with legacy code:

Jquery extension:

jQuery(function($) {

  var _oldShow = $.fn.show;

  $.fn.show = function(speed, oldCallback) {
    return $(this).each(function() {
      var obj         = $(this),
          newCallback = function() {
            if ($.isFunction(oldCallback)) {
              oldCallback.apply(obj);
            }
            obj.trigger('afterShow');
          };

      // you can trigger a before show if you want
      obj.trigger('beforeShow');

      // now use the old function to show the element passing the new callback
      _oldShow.apply(obj, [speed, newCallback]);
    });
  }
});

Usage example:

jQuery(function($) {
  $('#test')
    .bind('beforeShow', function() {
      alert('beforeShow');
    }) 
    .bind('afterShow', function() {
      alert('afterShow');
    })
    .show(1000, function() {
      alert('in show callback');
    })
    .show();
});

This effectively lets you do something beforeShow and afterShow while still executing the normal behavior of the original .show() method.

^{You could also create another method so you don't have to override the original .show() method.}