What is CSS-in-JS?

Defining CSS-in-JS is currently a polarizing topic in the JavaScript community. CSS-in-JS was born during the component age. The modern web is largely built with the component model. Pretty much all JavaScript frameworks have embraced it. As its adoption grew, more and more teams started working on various components of the same project. Imagine that you're working on a large app in a distributed team and each team is working on a component in parallel. Without having the team standardize CSS conventions, you're going to run into CSS scoping issues. Without some type of standardized CSS style guide, it's going to be easy for multiple teams to style a class name such that other unintended components are affected. Over time, a number of solutions emerged to solve this and other related problems with CSS at-scale.

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