If you are a React developer and want to build your React apps faster and more robustly, this course is for you. Learn to integrate TypeScript with React, boost your productivity, and create apps that are easier to maintain.

In this course, you will learn how to utilize TypeScript’s sophisticated type system to make React development faster and your code more readable. You will learn how to create component props, state, and events that are strongly-typed, allowing you to quickly understand what you can pass and helping you avoid mistakes.

Lastly, you will set up React projects with TypeScript. First, you will learn how to do this with the Create React App tool, then how to create a React and TypeScript project with Webpack and Babel.

Using TypeScript with React

```
type State = {
 count: number;
};
class CountDown extends React.Component<State> {
 constructor(props: {}) {
 super(props);
 this.state = {
 count: 10
 };
 }
 ...
}
```

```
type State = {
 count: number;
};
class CountDown extends React.Component<{}, State> {
 constructor() {
 this.state = {
 count: 10
 };
 }
 ...
}
```

```
class CountDown extends React.Component<{}, {count: number}> {
 constructor(props: {}) {
 super(props);
 this.state = {
 count: 10
 };
 }
 ...
}
```

We have a `CountDown` component that has no props but has a `count` state. How can we declare the `CountDown` component with strongly-typed `count` state and initialize it to `10`?

We have a <code>CountDown</code> component that has no props but has a <code>count</code> state. How can we declare the <code>CountDown</code> component with strongly-typed <code>count</code> state and initialize it to <code>10</code>?

```
class List extends React.Component<{data: string[]}> { ... }
```

```
class List extends React.Component<{}, {data: string[]}> { ... }
```

```
type Props = {
 data: any[];
};
class List extends React.Component<Props> { ... }
```

We have a `List` component that renders an array of strings in an unordered HTML list. Below is an example consumption of the component:

```
<List data={["fred", "bob"]} />
```

How can we define the type for the `data` prop in the `List` component?

We have a <code>List</code> component that renders an array of strings in an unordered HTML list. Below is an example consumption of the component:
<pre><code>&lt;List data={[&quot;fred&quot;, &quot;bob&quot;]} /&gt;
</code></pre>
How can we define the type for the <code>data</code> prop in the <code>List</code> component?

```
type Props = {
 data: string[];
 renderItem: (item: string) => React.ReactNode;
};
class List extends React.Component<Props> { ... }
```

```
type Props = {
 data: string[];
 renderItem?: (item: string) => React.ReactNode;
};
class List extends React.Component<{}, Props> { ... }
```

```
type Props = {
 data: string[];
 renderItem?: (item: string) => React.ReactNode;
};
class List extends React.Component<Props> { ... }
```

We have a `List` component that renders an array of strings in an unordered HTML list like in the last question. This component allows the consumer to optionally render the list items though.

Below are example consumptions of the component:

```
<List data={["fred", "bob"]} />

<List data={["fred", "bob"]} renderItem={item => {item}} />
```

How can we define the type for the `data` and `renderItem` props in the `List` component?

We have a <code>List</code> component that renders an array of strings in an unordered HTML list like in the last question. This component allows the consumer to optionally render the list items though.
Below are example consumptions of the component:
<pre><code>&lt;List data={[&quot;fred&quot;, &quot;bob&quot;]} /&gt;

&lt;List data={[&quot;fred&quot;, &quot;bob&quot;]} renderItem={item =&gt; &lt;i&gt;{item}&lt;/i&gt;} /&gt;
</code></pre>
How can we define the type for the <code>data</code> and <code>renderItem</code> props in the <code>List</code> component?

```
class Loading extends React.Component<{}, { message?: string }> {
 static defaultProps = {
 message: "Loading ..."
 };
 ...
}
```

```
class Loading extends React.Component<{ message?: string }> {
 static defaultProps = {
 message: "Loading ..."
 };
 ...
}
```

```
class Loading extends React.Component<{ message?: string }> {
 defaultProps = {
 message: "Loading ..."
 };
 ...
}
```

We have a `Loading` component that renders a loading spinner and an optional text message.

Below are example consumptions of the component:

```
<Loading />
<Loading message="Please wait ..." />
```

How can we define the type for the `message` prop and default it to `"Loading ..."` if it isn't passed into the component?

We have a <code>Loading</code> component that renders a loading spinner and an optional text message.
Below are example consumptions of the component:
<pre><code>&lt;Loading /&gt;
&lt;Loading message=&quot;Please wait ...&quot; /&gt;
</code></pre>
How can we define the type for the <code>message</code> prop and default it to <code>&quot;Loading ...&quot;</code> if it isn’t passed into the component?

We have a `CountDown` component that has an internal `decrementCount` method:

```
class CountDown extends React.Component<...> {
 ...
 decrementCount = () => {
 ...
 };
}
```

Would the following raise a TypeScript type error?

```
const counter = new CountDown(...);
counter.decrementCount();
```

We have a <code>CountDown</code> component that has an internal <code>decrementCount</code> method:
<pre><code>class CountDown extends React.Component&lt;...&gt; {
 ...
 decrementCount = () =&gt; {
 ...
 };
}
</code></pre>
Would the following raise a TypeScript type error?
<pre><code>const counter = new CountDown(...);
counter.decrementCount();
</code></pre>

Creating strongly-typed class components

Creating strongly-typed class components

This quiz will test what you have learned about strongly-typing class components.

Why TypeScript?

Using basic types

Creating types

Working with generic types

Creating strongly-typed function component props

Creating strongly-typed function component state

Creating strongly-typed class components

Creating strongly-typed component events and event handlers

Creating strongly-typed context

Creating strongly-typed refs

Creating React projects with TypeScript using Create React App

Creating a React and TypeScript project manually

Putting everything together

Quiz