If you have many props in an object, using Spread Operator makes it easier to pass them to the child component, but it's easy to lose control of them: The claim that using Spread Operator is antipattern is not 100% accurate. The Spread Operator is used to access all the elements within an Iterable: Important Note: the Spread Operator makes a shallow copy of the Iterable. DEV Community A constructive and inclusive social network for software developers. Once unpublished, all posts by arikaturika will become hidden and only accessible to themselves. If you have props as an object in React and want to pass them to the child component, you can use the Spread Operator to do so: You can even combine it with explicit props passing: Or override a property passed with the Spread Operator: It seems like using Spread Operator only brings benefits, shortening the code and making it more sophisticated, but that's not quite true. Let's look at some usage examples for this operator. It's not always obvious what the props we're passing have inside. Receive all new posts directly to your e-mail, No spam, only quality content twice a week, Let me know what you think about this article, Contact me and let's discuss any opportunities, // { name: "John", surname: "Doe", age: 18 }, // {"0": "s", "1": "t", "2": "r", "3": "i", "4": "n", "5": "g"}, // Prints ["John", "Andrew", "Ann", "Rose"], // Prints "{ minusOne: -1, minusTwo: -2, one: 1, two: 2 }", // Spreads array of numbers to a function arguments, // Prints {name: "John", surname: "Doe", age: 18}, // Prints {name: "John", surname: "Doe", age: 22}, To find out what is being passed, you need to scroll to where, If you forget that Spread Operator is used and add another property to, You can accidentally pass more props than necessary, It's hard to tell which props are actually being passed unless you use TypeScript. Sucrase playground link. You can avoid this problem by converting the Generator object to an array using Array.from() or array spread operator like [generatorObject].

For further actions, you may consider blocking this person and/or reporting abuse. Site made with React, Gatsby, Netlify and Contentful. By clicking Sign up for GitHub, you agree to our terms of service and Learning how not to write code is as important as learning best practices and design patterns. Let's change the App component code a bit to avoid using Spread Operator, but to explicitly pass the name and surname props: See how only one border, wrapping the entire App component appears. Most of the time we learn how to write code, we memorize best practices, design patterns, clean code principles, and that's perfectly fine, but learning how not to write code is no less important. This component is only responsible for outputting the name and the surname of the user to the screen. necessary (so React can spread them out as if they were positional args to Luckily, there's something called the spread operator - or spread attributes - that we can use, which only takes a few seconds to code! We pass our props like so: And our child component will use them like in the code below. https://babeljs.io/repl#?babili=false&browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=FAYw9gdgzgLgBAMTgXjgCgJQoHxwDwCG2A3gHTkDaAugL54D0RA3EA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&timeTravel=false&sourceType=module&lineWrap=true&presets=es2015%2Creact%2Cstage-2&prettier=false&targets=&version=7.3.3, https://github.com/notifications/unsubscribe-auth/AAAb2V-Vv--U8HfQQBqxWfTL8e9voKBEks5vQAlPgaJpZM4bGMwh, Fix implementation of JSX spread children, Fix implementation of JSX spread children (. See how both the App and User components are wrapped into the borders when they're updated, which means that both are refreshed when the button is clicked, which is wrong because the User component shouldn't be refreshed. Manager, Front-End Engineering at Factors.AI, Remember to whitelist your IP when you can't connect to Mongo DB , How web browsers work - the render tree (part 7, with illustrations) , Manipulating the DOM using Javascript - how to select nodes (part 1) . Let's call it ExampleComponentName. Another case is that you also can use spread operator to pass only parts of props to children components, then you can use destructuring syntax from props again. Regardless, I think it's within Sucrase's scope to just compile it and let other tools do the error checking, so this certainly seems reasonable to implement. Generator object should not be used as a child of React element. The text was updated successfully, but these errors were encountered: Interesting, I actually hadn't seen that syntax. Purchase includes access to 30+ courses, 240+ premium tutorials, 120+ hours of videos, source files and certificates. Keep in mind you might need to polyfill these features for older browsers. The component will now look like this. It's also useful when you're transplanting `children` from It's very useful when children components need lots of props but not want pass them one by one. If arikaturika is not suspended, they can still re-publish their posts from their dashboard. https://facebook.github.io/jsx/ includes it: Some history here: facebook/jsx#57 . and only accessible to Arika O. bugs in Babel than TSC so far since the switch in create react app 2.0 Sign up for a free GitHub account to open an issue and contact its maintainers and the community. right? You may convert it to an array with Array.from() or the [spread] operator before rendering. FWIW this is syntax that Typescript supported. My Let's take a closer look at App.jsx, specifically at the following lines of code: We know that the User component expects only two properties - name and surname, but we passed the entire state and added an extra counter, which causes the User component to be unnecessarily re-rendered since the counter isn't used, remember? During rendering, React may perform multiple iterations of iterable objects. Let's say we have a parent component called App which renders a child component called ExampleComponentDate. Updated on Jan 13, 2021. Interesting, I actually hadn't seen that syntax. In this case, nothing gets rendered and React outputs a warning message. Have a question about this project? You can see this happening in the example below: But what if we want, for example, to render a second child component and apply certain CSS styles to it? The child component will display a date we set in the parent component, so to be able to use it, it needs to get it from one level up (in this case) through props. ***> wrote: This rule applies when a Generator object is used as a child of React element. Looks like TypeScript is transforming it to React.createElement('div', null, a, b), which seems like it ruins the point of spread children. Important Note: For simplicity, we could have omitted curly braces and return in the User component, but we will keep them for now.

Yeah I'm using React. Download the videos and assets to refer and learn offline without interuption. privacy statement. TypeScript didn't implement that check, it seems. It will become hidden in your post, but will still be visible via the comment's permalink. notation: We can easily see that the more props we want to pass, the messier the code becomes. Built on Forem the open source software that powers DEV and other inclusive communities.

I just released a fix for this in 3.10.0. <. This drawback only applies to applications that do not use TypeScript. Once unsuspended, arikaturika will be able to comment and publish posts again. Templates let you quickly answer FAQs or store snippets for re-use. If you are not familiar with the "Highlight updates when components render" feature of the React dev tools, you can add console.log() to both components and check the console. Posted on May 3, 2020 With you every step of your journey. Later attributes override previous ones. While it's perfectly fine to use Spread Operator, you need to be very careful, as it's easy to accidentally pass unnecessary props, resulting in extra re-renders and greatly impacting the performance of the application. Please, donate a small amount. supported in React" (repl one place to another. Well occasionally send you account related emails. This modified text is an extract of the original, How to setup a basic webpack, react and babel environment, Detecting the type of Children components, React Boilerplate [React + Babel + Webpack], React.createClass vs extends React.Component. DEV Community 2016 - 2022. However, it's perfectly safe to use it with TypeScript because you get a quick overview of what props are being passed and get an error immediately if an unexpected property occurs. Successfully merging a pull request may close this issue. View with compliant examples side by side, View with noncompliant examples side by side, export class Hello extends React.Component {, {hello()} {/* REACT_BAD_CHILD_GENERATOR alarm because generator object is used as a child.

Are you using something other than React? They can still re-publish the post if they are not suspended. Today we will learn why Spread Operator is great, but better avoided when passing a set of props in React. The usage is equivalent to saying "Pass all these props to this component", and we complain that all properties are really passed, weird, isn't it? Looks like the original argument for adding it was for non-React use cases. Sign in First, let's learn or remember what Spread Operator does and why it's awesome. FWIW, Babel (with the React transform) throws an exception, saying "Spread children are not supported in React" (repl). We're a place where coders share, stay up-to-date and grow their careers. I am using destructuring to get the individual props so we can get rid of the props. There are a few things to remember about to get the most out of it. Already on GitHub? Let's create an application that contains two components: App and User. Today we learned why using Spread Operator to pass props to the child component in React can be considered antipattern: In any case, Spread Operator makes your code look more elegant and shorter, but remember to use it wisely. ([random example](, On Fri, Feb 22, 2019 at 7:14 AM Alan Pierce ***@***. A CSS, HTML junkie who codes with Carnatic BGM, sips coffee while planning Marathons, and does pushups while watching Darth Vader reign. Unlike other iterable objects such as array, Generator objects can be iterated only once. Like so: And our child component will access the properties of that object like this: I sometimes use this method for passing props but I'm not a big fan of it. createElement). Iterating an already iterated Generator object results in an empty iteration. Get monthly updates about new articles, cheatsheets, and tricks. Made with love and Ruby on Rails. This means we need to further inspect the code plus it can lead to unnecessary complexity when debugging. React Warning: Using Generators as children is unsupported and will likely yield unexpected results because enumerating a generator mutates it. Learn how. In React, passing props from parent to children components and using them is pretty straight forward. What we could do instead is store all the styles in an object and pass it from parent to child using the spread operator. This course explores all these topics, in addition to data hosting in Contentful and data fetching using Apollo GraphQL, Learn about Combine, the MVVM architecture, data, notifications and performance hands-on by creating a beautiful SwiftUI application, An extensive series of tutorials covering advanced topics related to SwiftUI, with a main focus on backend and logic to take your SwiftUI skills to the next level, An exhaustive catalog of React tutorials covering hooks, styling and some more advanced topics, A comprehensive series of tutorials covering Xcode, SwiftUI and all the layout and development techniques.

The order is important. React transform) throws an exception, saying "Spread children are not */}. Once unpublished, this post will become invisible to the public Donate to support families affected by the crisis. Our army protects all Europe from the occupiers and it needs help now to restrain one of the biggest armies in the world. We all try to be consistent with our way of teaching step-by-step, providing source files and prioritizing design in our courses. For example, in development mode, key validation accompanies an iteration. With this article, we are starting a new chapter called "React Antipatterns", which will consist of a few articles showing how not to write code in React and explaining why. Support Ukraine Donate to support families affected by the crisis, Learn how to make use of the spread operator. I think React wants you to pass an array there so it knows to check that you're using keys properly. But I think that restriction is something a linter should do (and a team should be allowed to opt in and out of), so I think it's fine to just allow and transform the syntax as specified in Sucrase. Antipatterns, just like patterns, have been around for a long time and it's worth learning and remembering them to avoid code smell. FWIW, Babel (with the You signed in with another tab or window.

My impression is Babel parses and recognizes it but intentionally disallows it for React, since they're worried that beginners will use it for dynamic arrays when really they should be specifying keys. Where each property needs to be passed as a single prop value you could use the spread operator supported for arrays in ES6 to pass down all your values. Personally, I like to think of this as an antipattern because it makes me triple check the code and make sure Spread Operator is needed in the particular component, which means that I use it wisely. Remember that the properties of the object that you pass in are copied onto the component's props. here are many ways to write bad code in React that are well known and should either be avoided or at least known about. I don't know why Babel chokes on this, though I've seen a higher rate of Passing each prop to that component might take a while, and it'll make the code harder to read. That's certainly what I'd expect. Are you sure you want to hide this comment? Generator objects are the return values of generator functions. Let's say we have a component that takes a lot of props. The look of our application is far from fancy, but the topic is not about the design, is it? array but know it's actually static and unchanging, so that keys are not We also use React.memo() to ensure that the User component is not unnecessarily re-rendered with the App. Ukraine was invaded by Russia in the early morning of 24.02.2022, explosions thundered in Ukrainian cities, many civilians died, tens of millions are affected.

The second drawback of this approach comes into play when you pass a lot of props to the child component - it's easy to get lost and spend a few minutes guessing what exactly is being passed, unless you use TypeScript and explicitly define what is expected by the child component. to your account. This rule was introduced in DeepScan 1.34.0. The firs example that came into my head was the CSS styles example but our variables can virtually contain anything we want. It is, nevertheless, very useful when children components need lots of props but we do not want to pass them one by one. Let's imagine our styles are stored inside multiple variables in the parent and we want to use them inside the second child. Developing web and mobile applications while learning new techniques everyday, Apply your Swift and SwiftUI knowledge by building real, quick and various applications from scratch, An extensive series of tutorials covering advanced topics related to React hooks, with a main focus on backend and logic to take your React skills to the next level, Concurrency, swipe actions, search feature, AttributedStrings and accessibility were concepts discussed at WWDC21. Once suspended, arikaturika will not be able to comment or publish posts until their suspension is removed. understanding of this syntax is that it's for places where you have an Image source: Christina Morillo/@divinetechygirl on Pexels. An overview of React Hooks and the frameworks you can use to build your React application blazingly fast, Create your first React project from the Terminal and save it on your local computer, Create your first JSX component using React, How to style your React components using inline styling, separate stylesheets or styled-components, Render different styles depending on different properties passed to your component, Learn about the basics of React Hooks, which introduced at React Conf 2018, Use the useState hook to manage local state in your React component, Manage with your component's lifecycle with the useEffect hook, Learn about the useRef hook, which replaces the JavaScript getElementById way, Learn about props in React to pass data from parent to child components, Render different UIs depending on different conditions and states, Load local JSON data into your React application, Learn the basics of asynchronous functions and promises by fetching data from an API using fetch, useEffect and useState, Learn how to toggle a state from true to false and back again, Create a hook to get the value and the onChange event of input fields, Create a static content-oriented website using React on Gatsby, Create your first NextJS React application, Learn how to create a React TypeScript application using the Create React App, Gatsby and NextJS methods, Learn the basics of TypeScript and how to use TypeScript in a React component, Create a custom hook to listen to the current window position of the user, Create a custom hook to listen to when an element is visible on screen, Manage global states throughout the entire application, Group multiple children together with React Fragments, Lazy Load heavy components to improve performance, Wait for data with React Suspense and React.lazy, Make environment variables secret with a .env file, Create a multiple-pages React application with Reach Router, Optimize a React application for search engines with React Helmet, Change the favicon's fill color depending on the user's system appearance, Implement props type-checking with PropTypes, Create a custom PropType using a validator function, Prevent unnecessary re-renders when the component stays the same, Detect the user's mouse position on a bound element, Connect the context and reducer with the frontend, Use gatsby-plugin-image for automatic image resizing, formatting, and higher performance, Toggle a modal visibility with a useOnClickOutside hook, Create a hook to determine the width and height of the window, Detect if the user scrolled to the bottom of the page, Store an item in a browser's local storage, Bring your website to life with beautiful 3D objects.