React + TypeScript [Syntax]

In this episode of Syntax, Scott and Wes talk about using React with Typescript — how to set it up, components, state, props, passing data, custom hooks, and more!

Freshbooks - Sponsor

Get a 30 day free trial of Freshbooks at freshbooks.com/syntax and put SYNTAX in the “How did you hear about us?” section.

Sentry - Sponsor

If you want to know what’s happening with your code, track errors and monitor performance with Sentry. Sentry’s Application Monitoring platform helps developers see performance issues, fix errors faster, and optimize their code health. Cut your time on error resolution from hours to minutes. It works with any language and integrates with dozens of other services. Syntax listeners new to Sentry can get two months for free by visiting Sentry.io and using the coupon code TASTYTREAT during sign up.

Linode - Sponsor

Whether you’re working on a personal project or managing enterprise infrastructure, you deserve simple, affordable, and accessible cloud computing solutions that allow you to take your project to the next level. Simplify your cloud infrastructure with Linode’s Linux virtual machines and develop, deploy, and scale your modern applications faster and easier. Get started on Linode today with a $100 in free credit for listeners of Syntax. You can find all the details at linode.com/syntax. Linode has 11 global data centers and provides 24/7/365 human support with no tiers or hand-offs regardless of your plan size. In addition to shared and dedicated compute instances, you can use your $100 in credit on S3-compatible object storage, Managed Kubernetes, and more. Visit linode.com/syntax and click on the “Create Free Account” button to get started.

Show Notes

04:55 - Components

Strategies
Example:

type Props = { value: string; } const App = (props: Props) =>

Return type? JSX.Element
FC or FunctionComponent
It’s discouraged for this reason: It means that all components accept children, even if they're not supposed to
It could be useful for a return type

12:13 - Props

Default props:

const defaultJoke: JokeProps = { joke: 'LOL JOE', id: 'YEAH', status: 200, }; function JokeItem({ joke = defaultJoke }: JokeProps): JSX.Element { return (

{joke.joke} = {joke.id}

); }

Because props are always destructured, you often have to make a new type for your props. You can’t just type each argument by itself.

18:38 - State

Just like Generics, State can be inferred
If your type is simple and you’re using useState, it just works: const [user, setUser] = useState(null);

22:27 - useEffect

Nothing special required
Good use of void: If you want to use a Promise function but not worry about await or .then(), you can pop a void in front of it:

useEffect(() => { console.log('Mounted'); // getJoke().then(console.log).catch(console.error); void getJoke(); }, [getJoke]);

26:09 - Refs

Very similar to state however some interesting things with null: const ref1 = useRef(null!);
“Instantiating the ref with a current value of null but lying to TypeScript that it’s not null.”

29:33 - Custom Hooks

This is a great use case for Tuples

31:00 - Context

This is probably the most complex thing in this list
First define the types
Use generic to pass in types OR null
This can also be non-null if you have default values in createContext: const AppCtx = React.createContext(null);

35:21 - Events

The React events system is better than Vanilla JS
Can handle them inline and have it inferred: onClick={e ⇒ yeah(e.target)}

const onSetType = (e: React.ChangeEvent) => setType(e.target.value)

React has a bunch of events built in — many of them take a Generic argument so you can specify the type of element that triggered it. Handy for native API methods like play and pause.

39:27 - ForwardRef

Again use of to pass in forwarded ref type as param 1, Props types as param 2:

type Props = { children: React.ReactNode; type: "submit" | "button" }; export type Ref = HTMLButtonElement; export const FancyButton = React.forwardRef((props, ref) => ( {props.children} ));

41:30 - ESLint