React render and commit

What this means

React rendering has two beginner-level ideas. First, React calls your components to figure out what the UI should look like. Then React commits the needed changes to the browser.

In beginner terms, this topic answers one practical question: "What should I write, and why does React care about it?" Do not try to memorize the syntax first. First understand the idea, then connect the syntax to that idea.

Why it matters

This helps explain why components should stay pure. A component should mostly calculate UI from props and state, not perform random side effects while rendering.

When you build real React screens, this idea helps you decide where data should live, what the user should see, and what should happen after an interaction. That is why this lesson is part of the main path instead of being an optional detail.

Step by step

1. Notice the UI problem this topic solves. 2. Look at the smallest possible example. 3. Change one value and predict what should appear. 4. Run the example and compare the result with your prediction. 5. Use the practice task before moving on.

Small example

function Counter({ count }) {
  return <p>Count: {count}</p>;
}

Common mistake

Do not put side effects directly inside the render body, such as changing document.title or starting timers. Use effects for work that must happen after rendering.

Practice task

Add a console log inside a component and click a state button. Notice that rendering is React calling your function again.

Remember this

Render calculates UI; commit applies changes to the browser.