Observing show/hide events with jQuery.

HTML Code

<button id="btnShow">Show</button>
<button id="btnHide">Hide</button>
<div class="container">
<div id="foo">
    I am #foo
</div>
</div>
<div id="console">
</div>

CSS Code

.container {
    height:60px;
    margin:10px;
}
#foo {
    background-color:#eeeeee;
    width:150px;
    height:50px;
    text-align:center;
    font-size:20px;
}

JQuery Code

//The magic code to add show/hide custom event triggers
(function ($) {
	  $.each(['show', 'hide'], function (i, ev) {
	    var el = $.fn[ev];
	    $.fn[ev] = function () {
	      this.trigger(ev);
	      return el.apply(this, arguments);
	    };
	  });
	})(jQuery);

//on Show button click; show the #foo div
$('#btnShow').click(function(){
   $('#foo').show();
});

//on Hide button click; hide the #foo div
$('#btnHide').click(function(){
   $('#foo').hide();
});

//Add custom handler on show event and print message
$('#foo').on('show', function(){
    $('#console').html( $('#console').html() + '#foo is now visible'+ '<br>'  )
});

//Add custom handler on hide event and print message
$('#foo').on('hide', function(){
    $('#console').html( $('#console').html() + '#foo is hidden'+ '<br>'  )
});

[출처] https://www.viralpatel.net/jquery-trigger-custom-event-show-hide-element/