@function
The
@function at-rule defines CSS custom functions. These custom functions are reusable blocks of CSS that can accept arguments, contain complex logic, and return values based on that logic. 
A Complete Guide to Bookmarklets
Browsers don't just let you bookmark web pages. You can also bookmark JavaScript, allowing you to do so much more than merely save pages.
Next Level CSS Styling for Cursors
Custom cursors with CSS are great, but we can take things to the next level with JavaScript. Using JavaScript, we can transition between cursor states, place dynamic text within the cursor, apply complex animations, and apply filters.