What happens when you call this.setState() in a React component?

What happens when you call this.setState() in a React component?

• A. It updates the DOM directly without re-rendering.
• B. It automatically calls render() after the state changes.
• C. It schedules the update and renders later.
• D. It can cause an infinite loop if used in render.

Answer: (B)

Calling this.setState triggers React to schedule a state update for the component. It does not touch the DOM directly. After React processes the update (often in the next event loop tick and sometimes batched with other updates), it calls render to compute the new UI and then applies the changes to the DOM. This is why the outcome is that a render happens after the state changes. Remember that state updates can be asynchronous and batching may occur, so the update isn’t guaranteed to happen immediately; if you need to run code after the update, you can use the setState callback or the updater form.

Calling this.setState triggers React to schedule a state update for the component. It does not touch the DOM directly. After React processes the update (often in the next event loop tick and sometimes batched with other updates), it calls render to compute the new UI and then applies the changes to the DOM. This is why the outcome is that a render happens after the state changes. Remember that state updates can be asynchronous and batching may occur, so the update isn’t guaranteed to happen immediately; if you need to run code after the update, you can use the setState callback or the updater form.