freeCodeCamp/curriculum/challenges/english/03-front-end-development-libraries/react/set-state-with-this.setstate.md

---
id: 5a24c314108439a4d4036173
title: Set State with this.setState
challengeType: 6
forumTopicId: 301412
dashedName: set-state-with-this-setstate
---

# --description--

The previous challenges covered component `state` and how to initialize state in the `constructor`. There is also a way to change the component's `state`. React provides a method for updating component `state` called `setState`. You call the `setState` method within your component class like so: `this.setState()`, passing in an object with key-value pairs. The keys are your state properties and the values are the updated state data. For instance, if we were storing a `username` in state and wanted to update it, it would look like this:

```jsx
this.setState({
  username: 'Lewis'
});
```

React expects you to never modify `state` directly, instead always use `this.setState()` when state changes occur. Also, you should note that React may batch multiple state updates in order to improve performance. What this means is that state updates through the `setState` method can be asynchronous. There is an alternative syntax for the `setState` method which provides a way around this problem. This is rarely needed but it's good to keep it in mind! Please consult the [React documentation](https://facebook.github.io/react/docs/state-and-lifecycle.html) for further details.

# --instructions--

There is a `button` element in the code editor which has an `onClick()` handler. This handler is triggered when the `button` receives a click event in the browser, and runs the `handleClick` method defined on `MyComponent`. Within the `handleClick` method, update the component `state` using `this.setState()`. Set the `name` property in `state` to equal the string `React Rocks!`.

Click the button and watch the rendered state update. Don't worry if you don't fully understand how the click handler code works at this point. It's covered in upcoming challenges.

# --hints--

The state of `MyComponent` should initialize with the key value pair `{ name: Initial State }`.

```js
assert(
  Enzyme.mount(React.createElement(MyComponent)).state('name') ===
    'Initial State'
);
```

`MyComponent` should render an `h1` header.

```js
assert(Enzyme.mount(React.createElement(MyComponent)).find('h1').length === 1);
```

The rendered `h1` header should contain text rendered from the component's state.

```js
async () => {
  const waitForIt = (fn) =>
    new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
  const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
  const first = () => {
    mockedComponent.setState({ name: 'TestName' });
    return waitForIt(() => mockedComponent.html());
  };
  const firstValue = await first();
  assert(/<h1>TestName<\/h1>/.test(firstValue));
};
```

Calling the `handleClick` method on `MyComponent` should set the name property in state to equal `React Rocks!`.

```js
async () => {
  const waitForIt = (fn) =>
    new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
  const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
  const first = () => {
    mockedComponent.setState({ name: 'Before' });
    return waitForIt(() => mockedComponent.state('name'));
  };
  const second = () => {
    mockedComponent.instance().handleClick();
    return waitForIt(() => mockedComponent.state('name'));
  };
  const firstValue = await first();
  const secondValue = await second();
  assert(firstValue === 'Before' && secondValue === 'React Rocks!');
};
```

# --seed--

## --after-user-code--

```jsx
ReactDOM.render(<MyComponent />, document.getElementById('root'))
```

## --seed-contents--

```jsx
class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      name: 'Initial State'
    };
    this.handleClick = this.handleClick.bind(this);
  }
  handleClick() {
    // Change code below this line

    // Change code above this line
  }
  render() {
    return (
      <div>
        <button onClick={this.handleClick}>Click Me</button>
        <h1>{this.state.name}</h1>
      </div>
    );
  }
};
```

# --solutions--

```jsx
class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      name: 'Initial State'
    };
    this.handleClick = this.handleClick.bind(this);
  }
  handleClick() {
     // Change code below this line
    this.setState({
      name: 'React Rocks!'
    });
    // Change code above this line
  }
  render() {
    return (
      <div>
        <button onClick = {this.handleClick}>Click Me</button>
        <h1>{this.state.name}</h1>
      </div>
    );
  }
};
```