The React's state

Besides the flexibility of decoupling your development with reusable components, another powerful feature of React is in its component state. Every React component comes with an internal state.

If the state of a component changes, the render method will fire and re-render the component. One thing that's very different from other frameworks is that React will re-render only the changes and nothing else.

Also, it does so in a very efficient way, and it doesn't have to touch the DOM for searching before making any changes. What is happening in the back is that JSX actually represents the DOM in JavaScript, and all the updates are happening on the script site in memory first; then it will do some checks, then batch the changes and, finally, it will commit them to the DOM.