Does React Guarantee the Order of State Updates?

Does React Guarantee State Update Order?

React optimizes performance by potentially performing state updates asynchronously and in batches. However, it's crucial to understand that:

For Updates in the Same Component:

• React guarantees that state updates for the same component are processed in the order they are called, even within a single event handler.

For Updates in Different Components:

• React 17 and Earlier:

  • Only updates within React event handlers are batched by default.
  • State updates outside event handlers are processed immediately.
  • This could lead to intermediate state when non-event handlers call setState() within a loop.

• React 18 and Later:

  • All updates are batched by default.
  • React maintains the order of updates across different components within a single batch.

Batching Effects:

• When updates are batched, React defers re-rendering until the end of the batch.
• This prevents unnecessary re-renderings and improves performance.
• Within a batch, the final state depends on the order of updates. The most recent update for a specific state key overrides previous ones.

Avoiding Intermediate States:

• Use the Functional Form of setState(): To avoid relying on the intermediate state within a batch, use the functional form of setState() that provides access to the previous state.
• Force Batching: In React 17 and earlier, use the ReactDOM.unstable_batchedUpdates API to force batching outside of event handlers. This is no longer necessary in React 18.

Conclusion:

React ensures the order of state updates for both the same and different components. The introduction of default batching in React 18 further simplifies state management and enables consistent behavior across event handlers and non-event handlers.

The above is the detailed content of Does React Guarantee the Order of State Updates?. For more information, please follow other related articles on the PHP Chinese website!