← flaviocopes.com

Using useState with an object: how to update

Published Oct 26 2020

When a state variable defined with useState is an object with properties you add / update, it’s somewhat confusing how to update it.

You can’t just update the object, or the component won’t rerender.

A pattern I found involves creating a temporary object with one property, and use object destructuring to create a new object from the existing 2 objects:

const [quizAnswers, setQuizAnswers] = useState({})

...

const updatedValue = {}
updatedValue[quizEntryIndex] = answerIndex
setQuizAnswers({
  ...quizAnswers,
  ...updatedValue
})

The same technique can be used to remove a property:

const copyOfObject = { ...quizAnswers }
delete copyOfObject['propertyToRemove']

setQuizAnswers({
  ...copyOfObject
})


Wanna go from noobie to expert?

I wrote an entire book on this topic 👇

© 2023 Flavio Copes Flavio Copes using Notion to Site Notion to Site. Follow on Twitter

Solopreneur? Wannabe? Adventure awaits