React + TypeScript


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!

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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} = {}
  • ); }
    • 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(}
    const onSetType = (e: React.ChangeEvent) => setType(
    • 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

    • Typescript-react is good
    • Extend your own
    • Most JS rules apply to TS

    46:20 - React as Global React 17

    • Also add JSX: True to eslint globals for typing things like JSX.Element
    • global.d.ts
    import * as react from "react" import * as react_dom from "react-dom" declare global { type React = typeof react type ReactDOM = typeof react_dom }

    48:08 - TSConfig

    • jsx: "react"
    • React emit .js files with JSX changed
    • Preserve .jsx file output
    • React-native → .js files with jsx not changed

    53:05 - Frameworks?

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