Skip to content

Using useState with an object: how to update

New Course Coming Soon:

Get Really Good at Git

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
})
Are you intimidated by Git? Can’t figure out merge vs rebase? Are you afraid of screwing up something any time you have to do something in Git? Do you rely on ChatGPT or random people’s answer on StackOverflow to fix your problems? Your coworkers are tired of explaining Git to you all the time? Git is something we all need to use, but few of us really master it. I created this course to improve your Git (and GitHub) knowledge at a radical level. A course that helps you feel less frustrated with Git. Launching May 21, 2024. Join the waiting list!
→ Get my React Beginner's Handbook
→ Read my full React Tutorial on The Valley of Code

Here is how can I help you: