So, to get around that, we can do a deep clone of props with a cloneObject() function that I outlined in one of my previous articles. It will look something like this. React ships with a bunch of pre-defined hooks. Well, TS sees the function as being bound at the point when the component is mounted. You will find this article useful if you are looking for a quick primer on the new patterns of React Router. They say things like, "default values are already handled in the function signature". And if we neglect to list requiredString in the function signature, it simply won't be available anywhere within the function. Your email address will not be published. We can render a new React component on click if we set a state so that the component can be rendered. If you like the content of this blog, subscribe to my email list to get exclusive articles not available to anyone else. But it won't work for a TS/React component. One approach is to alter your tsconfig.json to disable strict mode and allow implicit any types. React defaultprops deprecated React functional component default props vs default parameters, (as per Dan Abramov, one of the core team), so for future-proofing it's worth using default parameters. While using defaultProps is the best practice at the moment, it looks like this will change in the upcoming versions of React. We'll start by installing the project with create-react-app(CRA). And I'll feel really silly for having burned several days trying to reinvent the wheel. But doesn't this leave the optional properties still defined with type string | undefined?? It's efficient. Now you're all set with the React. And that’s why you’re probably going to be using a darn lot of hooks in … Run the following commands in your terminal to create a new react app. Oh, cool! to an interface property, TS will append | undefined as part of the type definition. It has a big ecosystem of…, Hooks contains our logic code in our React app. appended to it). If you’ve been following the news in the React ecosystem, you’ve likely heard about the new React Hooks API available in React v16.8. In other words, the approach above works great when we're writing a "regular" TS function. For the time being, I think I have a working solution. The simplest way to define a component is to write a JavaScript function:This function is a valid React component because it accepts a single “props” (which stands for properties) object argument with data and returns a React element. React hooks make render props and HOCs almost obsolete and provide a nicer ergonomics for sharing stateful logic. But for me, it's huge. That all said, I'm a dyed in the wool C# programmer and would love to be pulling across the great parts of that to the JS world with TypeScript. Hooks#. FWIW, this is the open RFC thread that discusses (amongst several things) deprecating defaultProps on functional components. It could just be that something's not "clicking" right in my brain... [NOTE: A few days after this was posted, I came up with an improved/revised method. Thank you for outlining the class-based approach. More than 1 year has passed since last update. So that's kinda what led to this whole article. TS chokes on this because the split() function requires a type string | RexExp. For a long-time React guy, that just feels... wrong. It will be written in React. It also works with both client and server-side rendered apps. It would look like this: There's a lot to like here. (Great! When you first start doing React with plain-ol' JavaScript, it takes mere minutes to realize how you can set default values on the optional props. You probably have more C# experience than me, but I've done a good bit of it and enjoy it. And they all run into the same limitations. As for the last example you give, the one that deals with functional components, there's a whole section in this article that outlines that approach - and also explains why I did not choose to use it. After tinkering with many different configurations, this is what I came up with: Unlike the other attempts shown above, this one actually works. The reason that it doesn't do this by default is because this usually isn't what you want. Why does it do this?? That would look like this: With all of your configs disabled/relaxed, you can actually get the above code to run/compile. Second, I do like your approach. React hooks helps us to implement the stateful functional components. I'm not sure that it addresses the issue - but it's definitely intriguing. We have a button that runs the this.onClick method on click. Hooks are supported in @types/react from v16.8 up. And I should never have to write code that accounts for this possibility. We're a place where coders share, stay up-to-date and grow their careers. When you add ? And don't even get me started on the push to deprecate defaultProps for functional components. Oh, dear! For a function component, if you assign defaultProps inline, TS seems to infer all the correct things, e.g. If you try typing this out in your IDE, you'll notice that it does, for the most part, work - until you reach the point where you're trying to define default values on the optional properties. Hooks replaces the needs for many life cycle methods in general so it's important for us to understand which ones. It changes the showComponent state to true . I can think of two scenarios where the render prop pattern will still be very useful, and I'll share those with you in a moment. Therefore, if we want to set the default prop value when null is set, we can write: If count is falsy, and null is falsy, we’ll pass in undefined as the value of count . And for about a day-or-two, I really thought that this was the answer. Do not panic my friend, React has given us another hook we can use: But yeah, not if I'm going to spend hours of my life trying to explain to a compiler my perfectly logical structure. We haven't defined any of the arguments as props, and therefore, there is no props.children to render. And if your answer to coding problems in any language is to turn off strict mode or to relax the core config constructs... Well, let's just say that nothing in this article - or this entire site - is going to help you in any way. The important bit here is the canLike utility that takes a while to run. So TS will complain about the above code because it will realize that the props object does not correlate with the requiredString type of string. Because you can't run your programming life based on what might change in the language. Subsequently, the search for alternate solutions becomes... ugly. Just wanted to say this post really helped me out. While passing our own props, we also need to pass the default props send to the render props by react router. But I'm just outlining a progression-of-thought here.]. To set the title with it, we use the Helmet component with the title element inside. And I love the description of "trying to explain to a compiler". We passed in Foo into our withHook higher-order component so that we can use our hook in the withHook HOC. I see what you did there. When we switch components, we can switch the title of the document. I'm not gonna go through a tutorial on that here. And that started my descent down the rabbit hole. (They do not work inside class components.). Primarily, there's a significant fear that defaultProps will be deprecated for functional components. While the above code indeed "works" just fine, I found that things started to get wonky when I began adding functions inside the functional component. We can use it to add any element we can add in the head tag, including the title tag. There is another way to cast Javascript into TS types. But before we look at hooks, we will start off with a new route rendering pattern. It will be changed if the prop property is passed. Then we can make the Foo component show when this.state.showComponent is true . It complains that the props.optionalString object is possibly undefined - even though I clearly defined a default value at the top of the function. Once you destructure the props out of their original object, you lose that clear scoping. I only want to spell out the optional properties, and spreading ...props allows me to do that. While most React components receive their props from a parent component, it’s also possible to specify default props. Oh, dear! I got some learnin' to do.) This fails on two key levels: When React invokes a component, it doesn't supply the props to the components as an array of arguments. It has to do with implementing default values for component props in React/TypeScript. Like this: A number of javascript folks don't like the new keyword, no problem create a factory... 'PropsWithChildren' only refers to a type, but is being used as a value here. Assuming that you're not in favor of disabling TS's core strengths, the next step is to figure out how to get TS to "accept" that props object. The code editor i will be using and recommending is Visual Studio Code.Its lightweight, fast, has great extensions and theming support. Except... that doesn't work, does it? So I've been diving in eagerly. That's my specialty.) But in the last week-or-so, something really threw me for a loop. class Foo extends React.Component { render () { const { someHookValue } = this.props; return
{someHookValue}
; } } export default withHook (Foo); We passed in Foo into our withHook higher-order component so that we can use our hook in the withHook HOC. So that could look something like this: Except... that doesn't work, does it? React components are composable — with or without hooks. Made with love and Ruby on Rails. And at the point that the component is mounted, there has been no default value set for props.optionalString yet. No sooner did I start researching this pattern than I found out that there's a big push to deprecate defaultProps on functional components. Nevertheless, I pushed onward. React is a popular library for creating web apps and mobile apps. Hi Adam the closest I came to a solution that could satisfy your need is following and everything is nicely typecheck, with this solution you could put the destructured props inside an args object inside your component, And typescript has a Required type that does the same as your AllPropsRequired type. Hi Adam. Regardless of the twisted reasoning behind this, it does seem as though this deprecation might happen. --> Speaking of React conventions, object destructuring obliterates the near-universal React practice of referencing props.foo or props.children. What I'm trying to do is, in React/JS, a five-minute lesson. runs just fine. Nice to see that my random angry rants are finding people in the ether. It's entirely possible that, in several years, I'll be shaking my head over the time I wasted on this, because the RFC was never adopted and defaultProps are still readily available. (Great! In other words, we need to explicitly define what's in props. Then run npm i. But have you tried this approach? This is basically React 101. I'm right back to the drawing board. In fact the React TS typedefs know how to infer that a prop provided in a defaultProp structure implies that the prop is not actually required on the component: (FWIW I don't actually grok those typedefs, but I understand what they do.). I'm new enough to TS that I'll freely admit not being aware of it. React Hooks is a new addition to React which enables you to use state and other features of the library without having to create a class. It was dynamically added by TS because the optionalString parameter is defined as optional (i.e., with the ? I did make it to the end, but think I'd missed that you were so much closer in all of the "right!!" yuck.). It doesn't require explicitly defining props.children. With you every step of your journey. We can break down the type of Hooks you can use within ag-Grid into two broad categories - those that have lifecycle methods (such as Filters) and those that don't (such as Cell Renderers). Just for reference, I'm hoping you find a way around this, or someone posts a solution. We can make the state dynamic by passing in the state variable into the title prop. It also works with server-side rendered apps. But if your solution to TS problems is to disable the power of TS, then... don't use TS. Hooks flatten things out. That just feels ridiculous to me. (OK, not incredibly close - but, Asheville.) The first option will make ref1.current read-only, and is intended to be passed in to built-in ref attributes that React will manage (because React handles setting the current value for you).. What is the ! Therefore, the default prop value will be set. The React 17 RC has just been released, and defaultProps are still here, and I'm struggling to find references to discussions about it being deprecated soon. The above code obliterates the standard React convention of being able to call props.children. Setting a Default value … With a good interface, you can definitively type all the values that are expected in React's traditional props object. I'm with you :) I saw your post because I also think the removal of defaultProps on FCs is a mistake, and saw your link on the RFC comments. Open VS Code in the project root and navigate to To be clear, it's obviously just an RFC and it may never come to pass. The "real" solution for default props in React/TS? Save my name, email, and website in this browser for the next time I comment. So is this the end of the article? I specifically outline there why I chose to forgo that approach - because the current indication is that defaultProps will be deprecated on functional components. React Hooks. The only thing I find lacking in it, is the need to manually chunk those values into an args object (assuming you want them in a single object - like I do). In React, children is supposed to be something that you just get "for free". Much appreciated. But TS won't compile this. To solve this problem, we can set a default value to the prop using defaultProps, so that react renders it whenever we don’t pass a prop value from the parent component. I think I had kinda stumbled into a different way to handle that. The element prop is used as the container element/component. And yet, in React/TS, this seemingly-simple operation requires jumping through a ridiculous number of hoops. Suffice it to say that AllPropsRequired is a type that will make all the properties of some other generic interface required. We can create our own hooks…, Your email address will not be published. ... > Click me )}} export default App. Thank you for bringing this to my attention!! If you used classes in React before, this code should look familiar: The state starts as { count: 0 }, and we increment state.count when the user clicks a button by calling this.setState(). [Yeah, yeah - I get it. In this article. That's highlighted in part two of this series...]. It's not like I'm trying to migrate from JavaScript to Objective-C, or from JavaScript to C++. That's not insurmountable, but I gotta play with it for a bit to see if there's a slicker way of handling that... You could try something around these lines, whit this you would get a fully typed props object that you could use as you used to. I glad I'm not the only one have problems with this. And in TS, just as in JS, we can supply default values for optional parameters - right in the function signature. One thing I don't like about this approach is that I couldn't seem to get it to work unless I also defined default values inside defaultProps for the required props. So does that mean that when React Hooks are stable you wont need render props at all anymore? I've been wanting to get my feet wet in a TS project for awhile. Someone in the comments will say something like, "Why didn't you just use setDefaultProps()?" The defaultProps static property should be set to an object representing the default props for the component. For the 3 optional props, default values are assigned. To make updating the title of a React app easy, we can use the react-document-title package to do it. Free and Affordable Books for Learning JavaScript, The Best Books for Learning JavaScript Programming, Canadian Province Array and Select Element, React Tips — Rendering Lists, Dynamic Components, and Default Props, Add an Audio Player with Vue 3 and JavaScript, Add a Video Player with Vue 3 and JavaScript, Add Charts to Our JavaScript App with Anychart, Developing Vue Apps with Class-Based Components — Type Annotations, Developing Vue Apps with Class-Based Components — TypeScript, Superclasses, Hooks, and Mixins, Create a Full Stack Web App with the MEVN Stack, JavaScript Best Practices — No Useless Syntax. To illustrate the issue, I'm gonna take something from a plain-ol' JS component, and convert it into a TS component. Not sure if you read to the end of the article (and I totally understand if you didn't), but for the time being, I think that last "solution" is what I'm running with for now. I'm just starting to learn React and use Typescript for work and am doing a little research on Proptypes and I came across this article in the vast sea of articles. But with hooks, composing state and reactions to that state becomes far, far simpler. Oh, yeah - I'm definitely nodding along to everything you've written here. If you google around for things like "typescript default props functional components", you'll find a number of articles and Stack Overflow questions that (attempt to) address this same problem. Makes a lot more sense than doing it manually with my own custom partial. [DISCLAIMER: My dev experience is quite substantial, but I just started doing TypeScript, oh... about 3 weeks ago. I hope that's the case. It's easy for other devs to "grok". While you're there, you say to your tour guide, "In your language, how do I say 'thank you'?" Required fields are marked *. That may not be a big deal to some. useEffect. I'll probably outline that in a near-future post. When I'm combing through the logic in a component, I definitely want to have a clear indicator that a particular variable was passed into the component as a prop. : Hi, Craig, and thanks for the feedback. It compiles. Note: PropTypes package is used for type checking. In TS, we can infer data types right in the function signature. To use gooks in a class component, we can create a functional component that’s used as a higher-order component. Another "challenge" with the approach you've outlined here is that the requiredString and requiredNumber values only exist under the props object - but optionalString, optionalBoolean, and optionalNumber exist as standalone variables. It seems to me that interfaces are the "default" TypeScript way to handle these kinda situations. This may seem like a good thing, but it can cause headaches later on because TS will expect you to write a whole bunch of code that's tolerant of undefined values - even though you know that you manually set a value for the variable, and it will never be undefined. (Umm... OK. // autocomplete suggestions works fine (FINALLY! Cuz in my (final) example, my interface is defined as: But I think I like the React.FC way better. The most important are useState and useEffect. If I remove requiredString and requiredNumber from the defaultProps definition, TS complains about it. It will be written in React. There are these techniques for doing this in class-based components - but we're not going to switch everything over to class-based components over this one simple issue. Then there is this technique for doing this in a function-based component - but there's a ton of chatter that this will be deprecated - and I don't want to base the dev for a "green fields" project on something at significant risk of being deprecated. Inside MyTSComponent, the first thing I'm doing is creating a new object, based on the props, cast to the type AllPropsRequired. The following is known about it's life cycle: By default, React runs the effects after every render I was wrestling with this a lot until I found this pretty sane and simple approach from typescript-cheatsheets/react: This seems like it satisfies everything except your defaultProps concern, which seems like it's a really premature concern. At this point, I started to think of "other" ways that I could provide default values. I've actually built a helper function now that takes the existing props and a simple object that defines any default values and then returns it mapped to the Props type. Then we pass the hooks’s output value into the Component , which can be any component, including a class component. 2 comments Open Bug: [eslint-plugin-react-hooks] Constructions should be caught in default props/args #20248. indicator on every one of the properties. OIC. React's new "hooks" APIs give function components the ability to use local component state, execute side effects, and more.. React Redux now offers a set of hook APIs as an alternative to the existing connect() Higher Order Component. (Until I find some other edge case where everything gets borked up...) It looks like this: The first thing you see is the AllPropsRequired type. We can create higher-order components with hooks if we want to use hooks with a class component. React hooks props. If the component is wrapping other content, that content will be rendered with props.children. Consider this example: I've set a default value of 'yo' on props.optionalString. So to use React Hooks, we’ll build a component that by default shows some information and lets us update that information by clicking a button. It's actually not too much more verbose than using PropTypes.defaultProps. My sis now lives in your region. Still - that's not really that big of a deal. Honestly, at this point, I started getting pretty annoyed. defaultProps is a property in React component used to set default values for the props argument. In this post I'll cover all React Hooks: useState. We just wrap our component with the DocumentTitle component to set the title. We’ll use snippets from this class throughout the page. We can call external JavaScript functions from React components. If nothing was passed in (i.e., if the property is undefined), I set the value to its default. TS doesn't fully grok that. React is the most used front end library for building modern, interactive front end web…, React is a library for creating front end views. If I'm writing "bad" code, or buggy code, then of course, I'd love for any tool to be able to point that out. IMHO, it's still a little "ugly" - but not so much that it makes my dev eye start twitching. Imagine you travel to another country - one that speaks a language very similar to your own. I didn't realize it was you. You may be thinking, "If you want default prop values, why don't you just use the built-in functionality for defaultProps??" I'm doing this because every property either had a value passed in (if it was required), or it will have a default value added to it. DEV Community © 2016 - 2021. If there were plans to deprecate it, I think we'd see something in the docs, or the usage signature would change to Greet.UNSAFE_defaultProps in advance, as is the team's habit with things like UNSAFE_componentWillMount. ). I had no idea that existed. But I know that I'm not entirely alone in this. The full list of properties is spelled out twice - once in the interface, and once in the function signature. Lets see it in our example, Pass props to a component rendered by React Router v4, Its very easy to achieve in react router, Lets create a new route for passing props to the component. No! We'll need to account for the fact that all of the props are being passed into the component as a single object. There's an entire section in my article that covers defaultProps. Maybe, in the next week or two, I'll realize how silly this whole little journey was. If a prop has a default value, it should never be undefined. And I'm trying to do something that really should be drop-dead simple. React Hooks are fully supported within ag-Grid - please refer to our working example in GitHub. So now that we know that we must specifically define the props object being passed in, maybe we can do this? When using hooks and functional components, we no longer have access to React lifecycle methods like componentDidMount, componentDidUpdate, and so on. This means that when you change the active post, this.props.post is pointing to the wrong thing and the toggleLike call goes to the new post, not the one … First, thank you for showing me the Required type! It supplies them in a single object - the props object. I've been travelling a bit and not able to sit down and test this in my IDE. Default props are only set when undefined or nothing is passed in as the value of the prop. That's my specialty.) But props.optionalString is type: string | undefined. The Props interface is fairly "standard" - nothing too magical there. React acolyte, jack-of-all-(programming)trades, full-stack developer, // props is still an interface but it has behaviors as a class. Example. The stub of my JS component looks like this: Nothing fancy here. Let’s play with react hooks. : React.ReactNode to your props so no need to handle that prop yourself. React Hooks with ReactJS Tutorial, ReactJS Introduction, ReactJS Features, ReactJS Installation, Pros and Cons of ReactJS, AngularJS vs ReactJS, Reactnative vs ReactJS, ReactJS Router, ReactJS Flux Concept, ReactJS Animations, ReactJS Discussion, ReactJS Quick Guide, etc. And the tour guide points you to a dozen different web pages that all explain ways that you can try to say 'thank you' - with no definitive answer. We can render a new component on click if we set a state to make the component render. We have to list children in the function signature. Then we created a global function that we can call in our React components. That really sums up some of my frustrations here. The fact that this "problem" feels ridiculous to me doesn't do anything to help me solve the problem. It has to do with implementing default values for component props in React/TypeScript. That looks like this: This doesn't throw any TS linting errors. So I looked at applying them inside of the function itself.