Add or remove class with JQuery based on vertical scroll

A tutorial on how to use JQuery and CSS to change the appearance of the website when scrolling down.
(modified ) by

When scrolling down a website, I use JQuery to change the appearance of the <header> element. I like to make it smaller after a certain number of pixels. The best way to accomplish this is to use JavaScript / JQuery to change the class name for the <header> element. To make this script work, you must first load the JQuery library.

Loading the JQuery library is easy. Simply add the following line to your HTML file after the <footer> element. You can also add it to the <head>element to load it faster, but for best performance, load it just before it is needed.

<script src=""></script>
$(window).scroll(function() {
  if ($(this).scrollTop() > 150){
  } else {

This code invokes the .scroll() JavaScript event and then uses .scrollTop() to determine whether there are more than 150 pixels from the browser's top. If the number of pixels exceeds 150, add a new class name small to the header element. If the element has fewer than 150 pixels, remove the class name.

Then simply add additional CSS styles for header.small.

header { height: 50px }
header .menu a { height: 1.2em }
.small { height: 25px }
.small .menu a { height: 1em }

So simple, yet so effective. :)