After all, we’re using React — the recommended approaches are to split up the logic of your app into as many components as possible and to use functional programming instead of imperative programming. You can consult the, An understanding of importing, exporting, and rendering React components. But conditional rendering? Use JavaScript operators like if or the conditional operator to create elements representing the current state, and let React update the UI to … Rendering Multiple Components Next Lesson This curriculum was created by Alex Chaffee and Burlington Code Academy, with significant contributions from Joshua Burke, Robin Hrynyszyn, Robin Rainwalker, and Benjamin Boas. Let's start talking about conditional rendering, multiple times you will need to render something in React based on a condition and if the condition is false render a different thing. This post was originally published several years ago, before the stable release of the Hooks API, and we just updated it a few months back. For situations where there is only one expected outcome, the “short circuit evaluation” is possibly most applicable. In other words, inside an IIFE, we can use any type of conditional logic. Then, you can render only some of them, depending on the state of your application. For example, here’s how you define one in TypeScript: JavaScript doesn’t support enums natively, but we can use an object to group all the properties of the enum and freeze that object to avoid accidental changes. If the user is logged in, it will display a Logout button. The logic will need to be moved outside of the render() method. That’s what allows React to correctly preserve the state of Hooks between multiple useState and useEffect calls. Sign up for Infrastructure as a Newsletter. The conditional (ternary) operator is the only JavaScript operator that takes three operands. As shown previously, you can conditionally return different markup from a component based on set conditions using an if…else statement. Generally, this is how you define and execute (at a later point) a function: But if you want to execute the function immediately after it is defined, you have to wrap the whole declaration in parentheses (to convert it to an expression) and execute it by adding two more parentheses (passing any arguments the function may take). You can decide which one is best for your situation based on: And, all things being equal, always favor simplicity and readability. To do so we have multiple options. Do not change the position of components arbitrarily in order to prevent components from unmounting and remounting unnecessarily. Notice that the method renderInputField returns an empty
element when the app is in view mode. This tutorial covers the most popular ways to implement conditional rendering in React: We’ll also review some tips and best practices for implementing conditional rendering in React, including: To demonstrate how all these methods work, we’ll implement a component with a view/edit functionality: You can try and fork all the examples in JSFiddle. You can conditionally assign elements or components to these variables outside the JSX and only render the variable within JSX. This code would display the Logout button if isLoggedIn is true, otherwise it would display nothing. In this article, you examined seven ways to implement conditional rendering in React applications. Supporting each other to make an impact. One of such libraries is JSX Control Statements. As with most things in programming, some are better suited than others depending on the problem you’re trying to solve. Our component has an all-or-nothing behavior, where nothing is rendered in place of the drawer if the expanded state property is false. IFFEs is a JavaScript function that runs as soon as it is defined: With this technique, you are able to write conditional logic directly within JSX but wrapped within an anonymous function that is immediately invoked on the evaluation of that code. { condition && jsx elements } For this article, I’m going to borrow the concepts of the EitherComponent. Maybe in this simple example, the performance improvement is insignificant, but when working when big components, there can be a difference. In Vue, we need to use v-if directive to render … Let’s review another technique that can help improve the code. Note: It would be more practical to apply the switch statement method when there are more than two possible values or outcomes. We return a element for each item. Open the App.js file in your code editor, scroll down to the render() method and make the following highlighted code changes: This is the process of creating an extracted function. The caveat, however, is that there is a limit to what can be done within such braces. Rendering with If / Else Inline Conditionals Logical && Ternary Operator Oftentimes when building with React, we will want to display different elements depending on the state of the application. Now, let’s consider if you were to attempt to use multiple returns in the render() method instead: Warning: This is an example of poorly performant code that should be avoided. Modernize how you debug your React apps — start monitoring for free. Conditional rendering is a term to describe the ability to render different user interface (UI) markup if a condition is true or false. This usually happens with the useEffect hook. https://blog.hackages.io/conditionally-wrap-an-element-in-react-a8b9a47fab2 Write for DigitalOcean This is how you can use forms to React. This function will return another function that will take the original component to return a new one: The component (function) returned by this inner function will be the one you’ll use in your app, so it will take an object with all the properties that it will need to work: The inner functions have access to the outer functions’ parameters, so now, based on the value returned by the function conditionalRenderingFn, you either return the EitherComponent or the original Component: This way, using the previously defined SaveComponent and EditComponent, you can create a withEditConditionalRendering HOC and, with this, create an EditSaveWithConditionalRendering component: You can now use it in the render method, passing all the properties needed: Conditional rendering can be tricky. In the same way, there’s an EditComponent: Now the render method can look like this: There are libraries like jsx-control-statements that extend JSX to add conditional statements like: This library is actually a Babel plugin, so the above code is translated to: Or the Choose tag, which is used for more complex conditional statements: These libraries provide more advanced components, but if we need something like a simple if/else, we can use a solution similar to Michael J. Ryan’s in the comments for this issue: Now that the save/edit functionality is encapsulated in two components, we can also use enum objects to render one of them, depending on the state of the application. b : c) As a final option, we can take advantage of the shorthand nature of the … I’m going to remove renderInputField and renderButton, and in the render method, I’m going to add a variable to know if the component is in view or edit mode: Now you can use the ternary operator to return null if the view mode is set, or the input field otherwise: Using a ternary operator, you can declare one component to render either a save or edit button by changing its handler and label correspondingly: As mentioned before, this operator can be applied in different parts of the component, even inside return statements and JSX, acting as a one-line if/else statement. We’ll start with the most naive implementation using an if/else block and build it from there. The logical && helps you specify that an action should be taken only on one condition, otherwise, it would be ignored entirely. { condition && jsx elements } { condition ? Conditional rendering in React in using the && operator In the examples presented above, we’re not using the else part of our conditionals to render something different. It’s 2020, function components with hooks are not an “alternative” way. We only want to render a h2 for the subtitle if it exists. Element variables are variables that hold JSX elements. Ternary operator (a ? You can see the complete code in the following fiddle: Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor. And replace the contents with the following lines of code: Next, open the App.css file in your code editor. For example, here’s how the logic to render the save/edit button could look with an IIFE: Sometimes, an IFFE might seem like a hacky solution. Final Words. Fragments allow you to return multiple elements by grouping them without adding an extra node to the document object model (DOM). That’s another story. Ok lets learn them. According to the Hooks documentation: Don’t call Hooks inside loops, conditions, or nested functions. We’ve added an editor’s note to clarify. You can check out our, Node.js installed locally, which you can do by following. Enum objects are a great option when you want to use or return a value based on multiple conditions, making them a great replacement for if/else and switch statements in many cases. Thanks for keeping us honest. You get paid; we donate to tech nonprofits. Here’s a good article about optimizing conditional rendering in React — I totally recommend you read it. If we have more than two branches that depend on the same variable to evaluate the condition, instead of having a big if/else block: Let’s look at some additional techniques to improve this code. ), and return whatever you want to render. 15 min read The application could be rewritten like this: Notice how this code conditionally assigns values - components - to AuthButton and then it can be referenced later in the JSX. For complicated comparisons and components, it may impact readability as a project grows. Your goal is to have only one of these buttons display. Back to our example, change the renderInputField method to look like this: One advantage of returning null instead of an empty element is that you’ll improve the performance of your app a little bit because React won’t have to unmount the component to replace it. You're not only going to learn about the theories, but you're actually going to put what you've learned into practice by creating React based applications. At some point, when building a React component, you'll run into a situation where you need to apply a class based on some condition. 1. An enum is a type that groups constant values. Why not just use constants? The render() method returns any of the following:. And replace the contents with the following lines of code: Then, run the application from your terminal window: And interact with the application in your browser: Each of the conditional rendering approaches will build upon this code. Element variables are similar to the approach to extract the conditional rendering into a function. Hacktoberfest For situations where there are two expected outcomes, an, For situations where there are more than two outcomes, a. Previously, the Login and Logout buttons were displayed. This concept is applied often in the following scenarios: In this article, you will examine seven ways to implement conditional rendering in React applications. Let’s try a simpler approach. In React, conditional rendering refers to the process of delivering elements and components based on certain conditions. For now, let’s continue to improve this example. Instead, always use Hooks at the top level of your React function. Conditional rendering in React works the same way conditions work in JavaScript. If the user is logged out, it will display a Login button. So let’s simplify it by extracting all the conditional logic to two render methods: one to render the input box and another to render the button. Here’s how the if/else block treats the component: And here’s how the short-circuit operator do it: How do you render multiple child components depending on a certain condition? Contribute to Open Source. React conditional rendering of multiple child components, Directly we can't return more than one elements. In cases where, this approach makes the component bloated, bulky, or less readable, you may encapsulate the conditional within a functional component: The ternary approach is useful for uncomplicated if…else evaluations. Let’s apply it to the example so you can see this in action. Change only the markup that is concerned with the conditional rendering. I’ll talk more about the performance implications of conditional rendering later. React conditional render multiple elements. It is special case and it will not be rendered. Otherwise, it will execute the actions contained in the else block. Conditional rendering in React works the same way conditions work in JavaScript. JSX uses curly braces ({ and }) to signify expressions that need to be interpreted prior to rendering. When you look at the console, however, you’ll see that componentDidUpdate is always called regardless of the value returned by render. Hub for Good And the function is executed within the JSX curly braces. render() The render() method is the only required method in the component lifecycle. Digesting React is a project-based introduction to React, the most popular JavaScript library for building reusable UI. As I showed you before, the performance of each option can be different. Based on the example of the article, I created two JSFiddles. For example, when trying the Fiddle that renders the empty
element, if you open the Inspector tab, you’ll see how the
element under the root is always updated: Unlike the case when null is returned to hide the component, where that
element is not updated when the Edit button is clicked: Learn more about reconciliation in React, which basically refers to how React updates the DOM elements and how the diffing algorithm works. The answer is by using fragments. The first part states the … React also allows you to handle multiple inputs on the form with ease. An understanding of JavaScript variables and functions. Swift and VR/AR hobbyist. You can’t put a condition that could prevent the hook from being called every time the component is rendered, like this: You have to put the condition inside the Hook: As with many things in programming, there are many ways to implement conditional rendering in React. You can use fragments with their traditional syntax: That said, when it comes to rendering multiple elements with fragments depending on a condition, you can use any of the techniques described in this article. The best practice is to keep components as simple as possible to avoid a wasted re-render of sibling or parent components. eherrera.net, Immediately invoked function expressions (IIFEs), Deciding how to implement conditional rendering in React, immediately invoked function expressions (IIFEs), optimizing conditional rendering in React, 11 alternative frameworks to Ruby on Rails, 11 database drivers and ORMs for Rust that are ready for production, Node.js, Express.js, and MySQL: A step-by-step REST API example, Managing network connection status in React Native, It doesn’t work with multiple/different conditions, How comfortable you are with JavaScript, JSX, and advanced React concepts (like HOCs). For example, if the first expression evaluates to false (false && …), it’s not necessary to evaluate the next expression because the result will always be false. Then, you can render only some of them, depending on the state of your application. There’s more than one way to use conditional rendering in React. LogRocket logs all actions and state from your Redux stores. Perhaps, you need to make an image bigger based on some state, or you need to make the image round instead of square based on a prop, or you want to truncate some text based on a user’s action. Next, revisit App.js and modify it to use the new component: This is the process of creating an extracted functional component. You’ll see how the Content component is treated differently by each implementation. It can also be applied in different parts of the component. An if…else statement will execute the actions contained in the if block when the condition is satisfied. Start with using create-react-app to generate a React App: Next, open the App.js file in your code editor. In this React tutorial, we’ll look into some basic expression rendering methods in the components JSX template including dynamic looping over the Object to create a list, using conditional expressions lie if; else and Switch case to manage multiple conditions. The only caveat is that you can’t conditionally call a Hook so it’s not always executed. React element variables. Use JavaScript operators like if, and let React update the UI to match them. In functional programming, the Either type is commonly used as a wrapper to return two different values. One thing I don’t like is having more than one return statement in methods, so I’m going to use a variable to store the JSX elements and only initialize it when the condition is true: This gives the same result as returning null from those methods. React render is one of the many component lifecycles that a React component goes through. It is the simplest way to do a conditional rendering in React. JSX is a powerful extension to JavaScript that allows us to define UI components. If showHeader evaluates to false, the
will be returned. However, this is not recommended because there are better, cleaner ways to achieve the same effect. It is possible to bypass these limitations with Immediately Invoked Function Expressions (IFFEs). This allows us to use if/else and switch statements inside return statements and JSX if you consider it to improve the readability of the code. Below, we loop through the numbers array using the JavaScript map () function. This can also be written in a slightly more concise manner using an arrow function: Certain libraries expose functionality to extend JSX, making it possible to implement conditional rendering directly with JSX. We use an if with our condition and return the element to be rendered. The ternary operator has a special case where it can be simplified. Ternary operator. We'd like to help. After installing the babel-plugin-jsx-control-statements package and modifying your Babel configuration, the application could be rewritten like this: However, this approach is not recommended as the code you write is eventually transpiled to a regular JavaScript conditional. Next, add some methods for handling input text and then save and edit events: Now, for the render method, check the mode state property to either render an edit button or a text input and a save button, in addition to the saved text: Here’s the complete Fiddle to try it out: An if/else block is the easiest way to solve the problem, but I’m sure you know this is not a good implementation. Let’s consider if you were to attempt to use an if…else statement in the render() method: Warning: This is an example of code that will not work properly. Each method has its own advantage and the choice of which to use is mostly dependent on the use case. So let’s start by defining a function that takes two arguments, another function that will return a Boolean value (the result of the conditional evaluation), and the component that will be returned if that value is true: It’s a convention to start the name of the HOC with the word with. However, most of the time, the differences don’t matter a lot. 2 minutes read Rendering React components is very important since it can make your app behave faster or slower, depending on your approach for rendering components, re-rendering components based on condition or state/props change. This operator is frequently used as a shortcut for the if statement. The same could be achieved with a switch statement where you can specify the markup for various conditions. What is Conditional Rendering? return isLoggedIn ? Generally, keep in mind the following recommendations: Bear in mind that these are recommendations and not rules. Handling authentication and authorization. It is probably always better to just write JavaScript than add an extra dependency over something so trivial. This is not necessary, however. This is what we call Conditional Rendering in ReactJS. React conditional render multiple elements. Let’s look at conditional rendering approaches to accomplish this. As a general rule, it is best to ensure that in implementing conditional rendering you: For more, see this article on high performing conditionals in React by Cole Williams. This code produces the same result as the renderAuthButton() approach. Conditional rendering in React works the same way conditions work in JavaScript. For loop. While developing an application in React or any other JS library/ framework, it is a common use case to show or hide elements based on certain conditions. Instead of guessing why problems happen, you can aggregate and report on what state your application was in when an issue occurred. First of all, we will have to add a “name” attribute to all the elements. You don’t have a lot of options with looping, either. So instead of having a class like this: You can use the useState hook to write the component with a function: Just like fragments, you can use any of the techniques described in this article to conditionally render a component that uses Hooks. Rendering with && Let's look at one of the most common cases: conditionally rendering a React element based on whether a specific prop exists or not. Applying this to our example, we can declare an enum object with the two components for saving and editing: And use the mode state variable to indicate which component to show. Editor’s note: This tutorial was last updated in October 2020 to reflect changes introduced in React 16.8 — namely, how to use React Hooks and Fragments for conditional rendering. The LogRocket Redux middleware package adds an extra layer of visibility into your user sessions. Like books, movies, and still trying many things. : ; How to Install Node.js and Create a Local Development Environment, this article on high performing conditionals in React, Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. But it doesn’t support loops or conditional expressions directly (although the addition of conditional expressions has been discussed before). Continue your learning with Higher Order Components and Conditional Rendering with HOCs. Using a Normal if The easiest way is to use a normal if inside our component code and return inside and outside the if. Revisi the AuthButton component and replace the if…else statement with a switch statement: Notice how this code returns various buttons based on the value of isLoggedIn. You can conditionally render jsx elements by using two methods. As the name implies, immediately invoked function expressions (IIFEs) are functions that are executed immediately after they are defined — there’s no need to call them explicitly. https://jsfiddle.net/eh3rrera/7ey56xud/embedded. In this tutorial we will walk through several of the options available. Consider a complex, nested set of conditions: This can become a mess pretty quickly. React.js is designed to make the process of building modular, reusable user interface components simple and intuitive. If you want to iterate over a list to render more than one component or implement some conditional logic, you have to use pure JavaScript. This tutorial was verified with Node v15.6.0, npm v7.4.0, and react v17.0.1. In React, it allows us to render different elements or components based on a condition. In this tutorial, we are going to learn about how to loop through array of elements in a react. It is presented as an example of the limitations of interpretation in the render() method. In React, you can have expressions like the following: If showHeader evaluates to true, the