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Merging Update Objects with …

Unlike the setState method in class components, useState does not automatically merge update objects. To do this you can combine the function updater form with the object spread syntax:
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const [state, setState] = React.useState({});setState(prevState => {  // Object.assign would also work
  return {...prevState, ...updatedValues};});
You may provide a function to compute the initial value of the state.
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const [state, setState] = React.useState(() => {
   const initialState = someExpensiveComputation(props);
   return initialState;});