Does React Guarantee Order of State Updates in Different Components?

Does React Maintain the Order of State Updates?

React performs state updates asynchronously and in batches for improved performance. However, the order in which state updates are applied can impact the behavior of your application. This article explores the order of state updates within and across components in React.

Same Component

Within the same component, React guarantees that state updates occur in the order they are called, ensuring that the latest update is always reflected in the component's state. This ensures consistency and prevents unexpected intermediate states.

Different Components

Similarly, React also maintains the order of state updates across different components. Even if state updates are triggered in different events, React preserves their order. However, it's important to note that React batches state updates within events, so the intermediate states may not be visible if updates occur inside the same event handler.

Intermediate States

The visibility of intermediate states depends on the React version and whether state updates occur inside or outside an event handler. In React 17 and earlier, updates outside event handlers were not batched by default, which could result in intermediate states being rendered. However, in React 18, all updates are batched by default, eliminating this potential issue.

Unstable API for Batching

React 17 introduced an unstable API, ReactDOM.unstable_batchedUpdates(), which allows developers to enforce batching of state updates outside of event handlers. However, this API is now deprecated and should be avoided in favor of the improved batching capabilities provided by React 18.

Conclusion

React guarantees that state updates are applied in the order they are called, regardless of whether they occur within the same or different components. This behavior is enforced by React's batching mechanism, which optimizes performance by combining multiple state updates into a single re-render. This ensures that the rendered state consistently reflects the most recent updates, providing predictable behavior and avoiding unexpected intermediate states.

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