Now my friend, the former one take an argument like this this.setState( (prevState)=>{ ...prevState, xyz:'somedata' } ), which means it depends on the previous state which will be passed to the function by react. On the other hand, this.setState( {...this.state, xyz:'somedata'} ) directly changes the master state. I hope you are getting the difference. The former one is safer as you can be sure that in case of a race condition, you can be assured that the state you are going to change is safe.