react function as child component typescript

Digital Transformation and Platform Engineering Insights, Difference between React Native CL-I and Expo, Visualizing with Graphical Processing Unit on Google Cloud, How to fetch data from firebase through seversiderendering Next Js. When button will be clicked, internal state of Toggle will change, and our, Here we define API type from implementation, which is a very powerful TS pattern (source of truth is implementation instead of manualy defined type. and also constraint our render method output within implementation, so we don't render things that aren't needed: Now with our last implementation of Card component, if consumers want to render just simple content, they need to write a lot of unnecessary markup: We can tweak our API to leverage both default children and children as an object map, so consumer would be able to use one or another. Well TypeScript doesnt allow exclusive union types. It should be already covered right? In this case, we need to define explicitly children prop, to make it required. State handling and logic is encapsulated within our, children is a function, which exposes public API of our component, which we can compose and render whatever UI we want . So instead of previous example, we should provide composable API like this: This composition is possible via children React Component props. We can achieve similar pattern in React by passing an Object map as children prop ( That's the beauty of React, it's mostly "just JavaScript" ). JSX element. JSX.Element is handy for restricting your children prop to React element but too limiting for general use. If youd like to get more web development, React and TypeScript tips consider The best up-to-date tutorials on React, JavaScript and web development. We can do better. Oh No Panic! To wrap up, use ReactNode for the children prop of your components unless you intend to make the prop more restrictive. for defining state. This is great indeed, but the API isnt very flexible as we have to always provide all props defined on children object map. Instead we should adhere to composition patterns, which were already familiar with, from old good HTML. No Errors Why Mister Anderson Why ? So how to prevent this? where I share things as I learn them.

JSX.Element is the most restrictive type you can use for children. Also we had to change type from, we add runtime check so app will throw when consumer forgot to provide children, here we are defining our children guards with TypeScript type guard capabilities, Consumer defines what should happen onToggle which will get actual value via function argument. It works only if your children prop is a single React element. The MERN Stack: Everything You Need to Know. Well, well get no compile nor runtime errors and our app will render with empty Card . First fix that may comes up my mind is to mark those as optional. ReactChild, Your first thought might be to allow an array of ReacChild items as well, using ReactNode, Declaring the children prop as ReactNode is a perfectly viable option, but if you want to trim your code even further, you can use React.FC. What about preventing consumer to define both render and children at one time? union types typescript useref usecontext Lets examine various parts of the implementation: Again both implementation and usage is type safe with top notch DX, without looking up any docs . This is definitely not what we wanted. As you probably guessed, FC stands for Functional Component. " All good! React and declarative composition is my favourite couple for building UI. In this post, Ill cover each of the types you can use and discuss the trade-offs so you can pick the right one for your use case. Lets have a look at our final Card implementation: Quite a lot is happening here, lets explain our code step by step: And now we can use both children patterns within our app: While previous patterns kinda mirror element projection that is available in HTML and with ShadowDOM via slot projection (of course not type-safe, in our case type safe ), we can go further and introduce more powerful patterns like Render props / Children as a function ! React.FC is a standard type for components written using the arrow function. Although intellisense for props defined within union is missing. This although broke constraints within Toggle implementation as both render and children are now defined without the need of conditional checks Which is wrong . In this article we will examine all possible/useful React children composition patterns backed up by TypeScript . This is tight coupling at its worst . Which wont protect us for use cases, when user completely forgets to define children or render prop. Happy coding! There is an open bug for it, so hopefully it will be fixed. ReactNode is the go-to type if you want the children prop to accept anything. ReactChild combined. props.children are baked within @types/react.d.ts definition and are marked as optional which mirrors React API behaviour. Just mentioning it here for curious reader . We use similar pattern for as we used in (2.) When I started using TypeScript with React, the first bump in the road was figuring out what type to use for the children prop. Thats because there are several different types React provides for this. Lets say that we have an application with a header and we want to place a navigation inside.

following me on Twitter, It didnt help that I saw multiple projects using different types interchangeably. ReactChild allows for primitive, so its a more permissive alternative to JSX.Element. However, ReactChild will not work with arrays. It wont work with anything else, including primitives, like strings: One more thing. Cheers! Client Side Gzip Compression using Webpack in React, (render)->
(render)-> , type Without = { [P in Exclude]? But the problem with this approach is that it doesnt allow mixing a single element with arrays: Learn on the go with our new app. Ok lets look on changes that we did within Toggle implementation: I dont recommend following pattern as its highly experimental and breaks guarantees within Toggle component implementation. So instead our API for Card could look like following: Were constraining children prop to be required and to have shape of an object map. As always, dont hesitate to ping me if you have any questions here or on twitter (my handle @martin_hotell) and besides that, happy type checking folks and till next time! children: ReactChild | ReactChild[]. In this article we will cover various patterns how to leverage children composition with TypeScript to get excellent developer experience and type-safety along the process. Also TypeScript will give us nice intellisense and compile time errors if we missed something, without need to browse docs of Card component . I , , , wake, & #oss #js #ts. Ok, last thing that we might want to do is to give consumer API flexibility by leveraging render prop instead of children. With that said I hope youve learned something new today and that youll leverage the power of React children composition with TypeScript sooner than later to provide consumers of your components with fantastic developer experience and type-safety . Love podcasts or audiobooks? Im referring to children prop that might be used with every React Component. Now we got proper compile errors if both children/render are defined at once, even so we got our intellisense back! here we define state via class property and we mark it as readonly again ( with that if you do this.state = {} within your code youll get compile errors as state is immutable ), private method which defines our API exposed via arguments in children function call, we double check if children is function, if not we throw ( runtime check ), finally we dont render any custom markup, instead were calling children with our public API, when children nor render are provided, we throw a runtime error . With that said here is our implementation: Now if consumers of our component forgets to define children, they will get compile time error : Now lets extends our Card API, by providing additional API like: Your initial thoughts about this API might look like following: Which is old good compound components pattern, which of course works, but in my opinion this is too much churn which is nicely solved with so called named slots projection API provided natively within browser via Shadow DOM (WebComponents). This page looks best with JavaScript enabled. By that prop union. So consumer of our Toggle should be able to write following markup: With How the API and usage should look like covered, lets implement our Toggle component which via children as a function pattern: Again, quite a lot code over there. sandbox children is a special prop, typically defined by the child tags in the JSX expression rather than in the tag itself. rendering Top five useful Chrome Dev Tools tips for React, Typescript: Five most useful utility types for React, Using React children prop with TypeScript, Web Development Tutorials - Iskander Samatov, React: Smart component API with conditional props and TypeScript, Compound Component advanced React pattern UI libraries love, GraphQL made simple with React Suspense and Hooks. Plus, the type is getting a little too verbose. We just need to add render with same annotation as children prop to our type Props definition: This is not correct though, as consumer of our component will get compile errors because both children and render are required. We have three React components App, Header and Navigation. React.FC. Lets build a simple Material design like Card component, which should be used like this: So we will leverage children props to render anything that will be provided between {PROJECTED CONTENT} tags. You can use the React.FC type on your arrow function components for brevity. We infer state type definition from implementation of initial state and we also map our state object to have all members readonly to avoid mutation on compile time. We can definitely write some runtime validation logic or we can leverage TypeScript and explicitly define Card component props API constraints. Principal Engineer | Google Dev Expert/Microsoft MVP | @ngPartyCz founder | Speaker | Trainer. It takes React elements, primitives, portals, fragments, etc. What needs to be done is to provide and exclusive ( XOR like ) operator to the language, which we can partially implement by conditional types. Curious reader may ask, where did we get this.props.children in our Card component implementation when we haven't defined any props ? this article uses following library versions: source code can be found on my github profile. Fix is quite easy, we can just make our children map to be optional with only content being required ( we don't wanna get empty cards within our UI ). Easy. But what if user forgets to provide children ? React.FC assigns the ReactNode type to the children prop, so you dont have to do it yourself. Good thing is that inference still works for function annotation for both children/render props! Look at this common use case of mapping to produce an array of elements: We learned how to build highly composable components thanks to props.children React API, which are really not that different from what we get from the browser platform ( Shadow DOM ), even so more powerful thanks to JavaScript. for this tutorial. When we would refactor. They have to be nested into each other so we end up with the following dependencies: While you may think, this is ok, its not. Also for those of you familiar with WebComponents, this is very similar to slot projection API, although much powerful as we have JavaScript at our disposal instead of static HTML . : never }, TypeScript doesnt allow exclusive union types, exclusive ( XOR like ) operator to the language, were leveraging union types to define our Component props API. I hope you found this post useful! With that API, our component should support one or another props pair. If you want to play around with the types yourself, heres a