I am a bit confused...Do companies use HTML/CSS and then add react.js to it or do they just use react JSX css only for building Websites?

CodePudding user response：

The html and css with js is almost always the final result. So some companies create first their mock-ups to see how it will be visualized in all the clients they desired to render( mobile desktop etc) and then break it in to components with any behavior they need. Other just take a mock-up and start directly in the frameworks they choose. All depends the money time and resources available.

CodePudding user response：

Normally companies are no longer working with plain HTML/JS/CSS anymore. That means that their use is restricted by the framework/library they are working with. In the case of React and other libraries to build SPA (Single Page Applications), it's a common pattern to use a single HTML file as an entry-point. Regarding JS and CSS they are normally used along with syntax extensions like JSX, libraries like styled-components etc, so they need to be transpiled and bundled to get them to work into the actual browser.