Introduction

React is just a humble library at ~2.8 kb. It consists of two parts.

• react package which is a diffing library (fancy term for some algorithm that is responsible to keep track of what changed, and perform an update based on that information).
• react-dom package, a chonker at ~39.4 kb responsible for everything DOM (document object model) related, and is meant to be paired with the react package.
• React is 100% independent from the browser and can be used outside it (for example on Mobile devices with React Native) because it is just a diffing algorithm.
• React DOM is to add the wrappers for the browser.

There are many ways to build a react app. The most common options include:

• Create React App
• Vite
• Next.js
• Gatsby

Unlike Angular, Vue, or Svelte that are more opinionated meaning they come with everything included out of the box such as state management, a router, perhaps a nice CLI (command-line interface) to bootstrap projects, and manage everything. React took a different approach. It’s completely unopinionated about those things. It doesn’t include a router, state management, or animation library so that you’re not limited to what the framework offers you. But, this can lead to analysis paralysis when having to choose one yourself. You have to determine what a popular package is for what you need, and try it out.

Reactivity is a programming paradigm that allows us to adjust to changes in a declarative manner.

• In the React example, if the state got changed it would rerender the component. You can find the most basic example of reactivity in a spreadsheet.