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
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
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
- 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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