What for it is necessary to push through ...prev in setState?

Question

React

Why do we need to add ...prev when changing the state, what's the point?

this.setState( prev => (  
            
                
                {
                    ...prev,
                    ...{
                    [e.target.name] : e.target.value
                    }
                }
                 
            )
          
        )

Answer 1

I do not see the point in such a record, it is enough to write

this.setState({
  [e.target.name]: e.target.value
})

https://reactjs.org/docs/state-and-lifecycle.html

Answer 2

This may be needed in applications where the state transition is actively used (For example, using Ctrl + Z, but such an entry is optional, SetState() will copy all the fields of the previous state to the new one)