How do I shrink a header on scroll?

Learn how to shrink a header on scroll with CSS and JavaScript.

Read on how to do it in this tutorial: https://www.w3schools.com/howto/howto_js_shrink_header_scroll.asp 

Try it yourself here: https://www.w3schools.com/howto/tryit.asp?filename=tryhow_js_shrink_header_scroll