Setting state in react has always been a tricky thing. There are many ways to do it, but most of them are anti-patterns, whereas only a few ways are correct and best practice.

Let's take a look at how to correctly set a react state in the scenarios of different data types.

Let's skip strings since those are trivial.

Numbers

Ignoring the case where we simply replace the number, updating a number state should be performed like this

setNumber(prev => prev + 1) //same for minus, multiple, divide, etc

Object states are set by using the spread syntax:

Objects

setUser(prev => {
  ...user,
  newKey: newValue,
  //OR
  updateKey: updateValue
})

Array states are set by "creating" a new array inside the setState and simply inserting the new element after the previous state of the array.

Arrays

setFruits(prev => [...prev, 'apple']) 
//or
setFruits(prev => [...prev, {name: 'Apple', price: 5}]) 

Conclusion

Setting states for different data types can get tricky, by using the best practices, always using the previous value, we can update the state using the proper methods.