react lifecycle 16.4 blog

getDerivedStateFromProps-react.js

static getDerivedStateFromProps(props, state) {
  if (state.value !== props.value) {
      return {
        derivedValue: deriveValueFromProps(props),
        mirroredProp: props.value
      }
     }
  // when null is returned no update is made to the state
  return null;
}

// after getDerivedStateFromProps the state looks like as follows:

//   {
//    derivedValue: someValue,
//    mirrordValue: newPropValue
//   }