how to filter elements with javascript???

Making a personal website and trying to showcase projects I've worked on and trying to make it filterable. But I can not for the life of me figure out how the javascript part works? W3schools has been amazing and digestible up until this point. Using this as my base but what do I replace in the java part to make it filterable???? https://preview.redd.it/a35guno7yt3h1.png?width=1990&format=png&auto=webp&s=169b5610856995b84e1cee0881dac68dbc8be32d submitted by /u/ToxicGhostJuice [link] [留言]