How do I implement getDerivedStateFromProps?

Posted by Prem Tiwari | Updated on

While you probably don’t need it, in rare cases that you do (such as implementing a <Transition> component), you can update the state right during rendering. React will re-run the component with updated state immediately after exiting the first render so it wouldn’t be expensive.

Here, we store the previous value of the row prop in a state variable so that we can compare:

This might look strange at first, but an update during rendering is exactly what getDerivedStateFromProps has always been like conceptually.

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