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. 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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 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? Next.js makes this a TREAT Gatsby just use .tsx extensions https://www.gatsbyjs.com/plugins/gatsby-plugin-ts-config/ Links https://github.com/typescript-cheatsheets/react Tanner Linsley https://github.com/wesbos/eslint-config-wesbos Deno Architect https://fav.farm/ Snowpack Vite Parcel 2 Foam ××× SIIIIICK ××× PIIIICKS ××× Scott: Obsidian Wes: Folding Allen Keys Shameless Plugs Scott: 1: Level Up Tutorials Pro Spring Sale - 50% off annual subscriptions! 2: SvelteKit Course Wes: Beginner Javascript Course - Use the coupon code ‘Syntax’ for $10 off! Tweet us your tasty treats! Scott’s Instagram LevelUpTutorials Instagram Wes’ Instagram Wes’ Twitter Wes’ Facebook Scott’s Twitter Make sure to include @SyntaxFM in your tweets