What is the purpose of callback function as an argument of setState ?

The purpose of using a callback function as an argument of setState in React is to ensure that certain code is executed only after the state has been updated and the component has re-rendered. This is crucial because setState is asynchronous, meaning it schedules an update to the component's state object and then continues executing the next lines of code without waiting for the state update to complete.

Here are the key reasons and scenarios for using a callback function with setState:

1. Guarantee of State Update: The callback function is called after the state update has been applied and the component has re-rendered. This guarantees that any code within the callback is working with the most recent state[1][3][4].

2. Sequential State Updates: In scenarios where the next state update depends on the current state, using a callback ensures that the updates are sequential and accurate. This prevents errors that might occur due to the asynchronous nature of setState, where consecutive setState calls might not reflect the intended state[2][5][7].

3. Post-Update Operations: If there are operations that need to be performed right after the state update and rely on the updated state, such as API calls or complex logic, placing these inside the callback ensures they execute at the correct time[1][3][4].

4. Avoiding Unnecessary Renders: While React batches state updates and minimizes unnecessary renders, using the callback can further control and optimize rendering behavior, especially in complex components[3][5].

5. Handling Side Effects: Similar to lifecycle methods like componentDidUpdate, the callback can be used to handle side effects that should only occur after ...