CSS in JS

In the community, everyone agrees that a revolution took place in the styling of React components in November 2014, when Christopher Chedeau gave a talk at the NationJS conference.

Also known as Vjeux on the Internet, Christopher works at Facebook and contributes to React. In his talk, he went through all the problems related to CSS at scale that they were facing at Facebook.

It is worth understanding all of them, because some are pretty common and they will help us introduce concepts such as inline styles and locally scoped class names.

The following slide, taken from the presentation, lists the main issues with CSS:

The first well-known problem of CSS is that all the selectors are global. No matter how we organize our styles, using namespaces or a BEM-like methodology, in the end, we are always polluting the global namespace, which we all know is wrong. It is not only wrong on principle, but it also leads to many errors in big codebases, and it makes maintainability very hard in...