For three years, I have styled my web apps without any .css files. Instead, I have written all the CSS in JavaScript. I know what you are thinking: “why would anybody write CSS in JavaScript?!” Let me explain. What Does CSS-in-JS Look Like?Developers have created different flavors of CSS-in-JS. The most popular to date, with over 30,000 stars on GitHub, is a library I co-created, called styled-com