I have to sometimes do this in useEffect to set a value properly. What exactly are we doing? Just using the previous value? When do you know when to do it exactly?
When you use call the setter with a function as parameter, like you did, the “prev” (the function argument) is the current state.
In your example, the “prev” is the current value of “data”.
You usually do that way instead of just setData(something) when you probably have state changes with a very short period and you want to make sure you are using the latest state value possible.
As setState is async, you may call it before other state change be completed and use old values. Using it with a parameter grants you using the latest state.
The only thing I don't get is the following line with hooks
handleChange = (name, value) => setData(prev => ({ ...prev, [name]: value }))I have to sometimes do this in
useEffectto set a value properly. What exactly are we doing? Just using the previous value? When do you know when to do it exactly?When you use call the setter with a function as parameter, like you did, the “prev” (the function argument) is the current state.
In your example, the “prev” is the current value of “data”.
You usually do that way instead of just
setData(something)when you probably have state changes with a very short period and you want to make sure you are using the latest state value possible.As setState is async, you may call it before other state change be completed and use old values. Using it with a parameter grants you using the latest state.
That makes sense thank you! :)