When to Use Functional `setState` in React?

When to Use Functional setState

React's setState function allows components to update their internal state, triggering a re-render of the component and its children. However, there are two different ways of updating state: the object method and the functional method.

Object Method

this.setState({pictures: pics})

This method is simple and easy to read. However, it has a potential issue with batching. React may batch multiple setState calls into a single update for better performance. If any of the setState calls use the same key, the value of the key from the last call will be used.

Functional Method

this.setState(prevState => ({
   pictures: prevState.pictures.concat(pics)
}))

This method uses a function to update the state. It takes the previous state as an argument and returns the new state. This allows you to access the previous state when updating the new state, which is helpful when you need to depend on the current state.

The functional method is generally preferred over the object method because it eliminates the issue with batching. It ensures that the state is updated properly even if multiple setState calls are made in the same render cycle.

Conclusion

When dealing with state updates, it is generally recommended to use the functional method of setState. This ensures that the state is updated properly and avoids potential issues with batching.

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