react.dev/content/docs/faq-state.md

---
id: faq-state
title: Component State
permalink: docs/faq-state.html
layout: docs
category: FAQ
---

### What does setState do?

`setState()` schedules an update to a component's `state` object. When state changes, the component responds by re-rendering.

### Why is `setState` is giving me the wrong value?

Calls to `setState` are batched, so it is possible to "lose" an update if you call it with the partial object syntax:

```jsx
incrementCount = () => {
  this.setState({count: this.state.count + 1})
}

handleSomething() {
  // this.state.count is 1, then we do this:
  this.incrementCount()
  this.incrementCount() // state wasn't updated yet, so this sets 2 not 3
}
```

See below for how to fix this problem.

### How do I do ordered state updates?

Pass a function instead of an object to setState to ensure the call always uses the most updated version of state (see below). 

### What is the difference between passing an object or a function in setState?

Passing an update function allows you to access the current state value inside the updater. Since `setState` calls are batched, this lets you chain updates and ensure they build on top of each other instead of conflicting:

```jsx
incrementCount = () => {
  this.setState((prevState) => {
    return {count: prevState.count + 1}
  })
}

handleSomething() {
  // this.state.count is 1, then we do this:
  this.incrementCount()
  this.incrementCount() // count is now 3
}
```

https://reactjs.org/docs/react-component.html#setstate

### Should I use a state management library like Redux or MobX?

[Maybe.](http://redux.js.org/docs/faq/General.html#general-when-to-use)

It's a good idea to get to know React first, before adding in additional libraries. You can build quite complex applications using only React.