React Fiber introduces a new lifecycle for processing updates and rendering components. This lifecycle consists of three main phases:
Render Phase: In this phase, React computes the new component tree based on the updates (e.g., new state or props). This phase is also known as the 'reconciliation phase.' During this phase, React can pause and resume the work as needed, allowing it to yield control back to the browser and maintain responsiveness.
Commit Phase: Once the render phase is complete, React moves to the commit phase, where it applies the changes calculated during the render phase to the DOM. This phase is also known as the flush phase. Unlike the render phase, the commit phase cannot be interrupted, as it involves making actual changes to the DOM.
Cleanup Phase: After the commit phase, React performs any necessary cleanup, such as unmounting components that are no longer needed, and running side effects like componentDidUpdate or componentWillUnmount.