Why Doesn't `setState` Update the React Component State Immediately?

Why calling setState method doesn't mutate the state immediately?

In your code, you're using the setState method to update the state of your component. However, you're not expecting the updated state value just after calling setState. This is because setState is an asynchronous method, and the state is not mutated immediately.

Asynchronous Nature of setState

setState is an asynchronous method because it needs to perform some tasks before updating the state. These tasks may include calling the render method and updating the UI. If setState were synchronous, these tasks would have to be completed before any other code could be executed, which could lead to performance issues.

Using a Callback Method

To check the updated state value just after calling setState, you can use a callback method. A callback method is a function that is executed after setState has completed its task. Here's an example:

this.setState({ barClubLounge: event.target.checked }, () => {
  console.log('updated state value', this.state.barClubLounge)
})

In this example, the callback method will be executed after the state has been updated, and will log the updated value of barClubLounge to the console.

Why is setState asynchronous?

setState is asynchronous to improve performance. If setState were synchronous, the browser would have to wait for the state to be updated before rendering the UI. This could lead to performance issues, especially for complex components that require extensive computations.

By making setState asynchronous, the browser can continue rendering the UI while the state is being updated. This results in a smoother and more responsive user experience.

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