React app loading twice. js, App is rendered twice.
React app loading twice Two effects run as a result of this render, including the one to send the api request. Perhaps this diagram would help. log(arr); return ( <p>test</p> ); } export default App; as you can see I use console. index. When the button is clicked, the selected item in the dropdown is added to the list. This occurs because since React 18, when Tweaking the performance of an App exposes some components using useState render twice. ) useQuery runs twice on initial load with React 18 TanStack/query#3633. StrictMode is a wrapper introduced in version 16. length > 0 && <RecipeList recipes={data}/>}. 0 it is applied also for hooks. At first it only happened on Class Components but now will be default for This doesn't work because React uses synthetic events which are reused when it’s handling is done. Some router component using built-in 'loader' prop makes the RouterProvider to render twice. In my opinion, this should only be outputted once but it is not. Specifically, implicitly calling the rendering related functions extra times. You don't need boucle of . StrictMode. If your component renders the same result given the same props, you can wrap it in a call to React. log('I am JOKER\'s useEffect--->', When installing the starter Ionic react app (example with tabs), IonApp renders twice. After migration it starts adding the analytics twice when we click on anchor tag. I also had the same issue. Your component has to be pure. function App() { const arr = ["one", "two", "three"]; console. That is exactly what useRef is for. log once for each variable and its log it twice the same thing with error If you've previously installed create-react-app globally via npm install -g create-react-app, we recommend you uninstall the package using npm uninstall -g create-react-app or yarn global remove create-react-app to ensure that npx always uses the latest version. If you move this. With the release of React v18, Strict Mode was extended with a new feature which brought some unusual behaviour. StrictMode> ); When you have the Strict Mode enabled (which you should), React performs additional runtime checks in the development environment to make sure your app is safe and sound. React, when is rerendering your component, see that and recycle that component. getElementById("root")); root. import ". Why? index. To do this, React will support remounting trees using the same component state used before unmounting. SettingsLoad. React Strict Mode. Also in the dropdown change method, that API should be called and will return maybe has returned value true (If has returned true, the Alert should be hide). I'm encountering an issue in my React app where the Title component is re-rendering twice when I click on a button in my App component. if you don't want it to do so you can disable StrictMode by removing the <React. 0 Steps To Reproduce create-react-app test-render --template typescript go to src/App. StrictMode> Basic React app is triggering useEffect twice [duplicate] Ask Question Asked 11 months ago. My issue is that the fetch request is being made twice on initial page load. As of version 18 this also includes every component getting mounted (causing useEffect to be executed), unmounted, and finally mounted again (causing useEffect to be executed (This is happening on an app I've created with the new recommended create-react-native-app (expo). When that happens, all the code in your function component is ran - including the ternary expression inside your JSX return value. In other words, StoryTray is not a pure function—running it Here in 2020, this was being caused by <React. StrictMode> component that was wrapped around the <App /> in new versions of Create React App. Example: useEffect(() => { console. Reload to refresh your session. Any thoughts? I have the following component where console. Is it supposed to render twice or can/should I optimize somehow? I’m trying to display Alert message if API return false. I really don't know what to look at next. the reason behind that is documented here The render function can be called almost any number of times before the commit phase occurs and updates are flushed to the DOM. I'm not sure I understand your question, but here goes. Here is render() with navbar rendered twice: React StrictMode intentionally call twice the constructor and others calls like render, componentShouldUpdate That makes more deterministic the execution of the component and shows side efects of safe and unsafe functions like constructor, render, componentWillMount, componentWillUpdate React version:18. The app loads up once, then the request completes, state is set, and the app reloads again - the entire page refreshes -which results in a flickering of the page, and generally bad Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. But I need it in my project. ReactDOM. js file. It must be the gameId that initially has no value (First call to useEffect) and gets populated by Match component of router library (Second call to useEffect). When the server needs more than 2min for answering the request is called again. js). I'm There is no other component present in the app. React rendering your component twice in dev mode to help with: - Identifying components with unsafe lifecycles - Warning about legacy string ref API usage - Warning about deprecated findDOMNode usage - Detecting unexpected side effects This app is created by CRA with typescript . 0) and im wanting to do some API calls and other logic in my app on render using useEffect. " but how come my code only logs out When using React’s useEffect hook in a Next. I am just setting up the first canvas for the Phaser. StrictMode in the application, react will render twice in development mode. To avoid this, you can comment out the <React. Best practices would be to move side effects (like window prompts) to a useEffect call. js file, I am invoking a console. The Real Housewives of Atlanta; The Bachelor; Sister Wives; 90 Day Fiance; Wife Swap; The Amazing Race Australia; Married at First Sight; The Real Housewives of Dallas You're calling a function in the template that is returned. Here is the code: The problem is, useEffect is triggered twice when I check with console. When using React's Strict Mode, To fix this issue, you can disable the StrictMode by removing the </React. 0) and componentDidMount executes twice. log in render method of both app as well as test component. css'; Your App component is rendered within React. I have added console. / it installs all If you're not running StrictMode (if you are, see answer by papacool: it's by design), when the code in the constructor is run twice, you can be sure that the component is being created anew two times. Every time you update state and props, your component will rerender but with power of hooks it remembers old state value and keeps state among consequent renders I want to load an incident banner link at the top of the page. memo(({ history }) => { When the component mounts, there is always one render. Now when I load the app I always get two on connection calls on the websocket server and the console also shows 'Component App is constructed' twice. Identifying components with unsafe lifecycles Apparently this is happening not only on react apps but on jquery app aswell, have a look here: Again when I try to load the image as background-image property of the css, the browser doesn't cache the image and load it twice. (npx comes with npm 5. tsx write useEffect( ) in the function before return, such as "console. Load 7 more related questions Show fewer related questions Sorted by: Reset to I am using react-router's route loader feature to fetch data before the page is loaded. config. From docs: why is called twice. javascript; image; dom; browser-cache; preload; Share. log() twice for everything. and when I console. render( <App />, document. Instead use the componentDidUpdate lifecycle function to log when state or props update. keys(data). But StoryTray directly modifies the stories array from the props. It runs once if i navigate to the page. Function-components are not meant to deal with data calculations, and that sort of things, function-components are Recently, I have moved my app from react 17 to react 18. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company You are using <StrictMode/> and it's development mode. css"; import Phase Its not remounting. To do this, React would unmount and remount trees using the same component state as before. React Components render twice - any way to fix this? if you used create-react-app and run your app with yarn start you To get the user details into my react app, I make fetch calls and can get the data no problems. js, App is rendered twice. 1. So every time you click after the first time, the state goes from 1 -> 1 and you get I was debugging a React app and noticed that some of my functions were called multiple times in a way I could not explain. this behavior might be because StrictMode whitch renders components twice (on dev but not production) in order to detect any problems with your code and warn you about them (which can be quite useful). Go to index. I have no idea why it show me 2 copies of header and footer. So, its re-render your whole component twice so you can easily check the result. js during development to help you write better React components. 6. Follow edited Nov 9, 2016 at 16:42. React. StrictMode> ); I did try using the useRef method but I was advised by my staff to not use this specific method and try another possible outwork. I don't think that this is a Cross-Origin Resource Sharing (CORS) preflight issue, because this happens only for requests with long response times. ****PLUS***** I checked React dev tools Profiler to check the component is really rendered twice when a button is clicked and state is changed. The reason for the double alert will be that some props or state is changing, causing your component to rerender. js and comment strict mode tag. You switched accounts on another tab or window. I needed to do 'dispatch' to load global settings for the app. couple of save options, i restricted with unique key column at database level, but few tables still need to handled at code level. I initially thought it was some sort of "developer feature" and tried to run a build, and all I could see if that the APIs that should not be called were called once instead of twice: for me, this is because of React. Contact. But only in FF, Chrome, NOT in IE11. I created a new react app with npx create-react-app after all installation finished I started the application but its keep on reloding, I tired all solution on the internet but nothing fix the issue. The problem with your implementation is that you are setting your user state once components are rendered (you are setting the user state using useEffect in App. To Reproduce Steps to reproduce the behavior: Run storybook alongside an application based on create-react-app. log the data in my render React. This is an Admin portal that uses the company's Azure Active Directory to When using React. Then you bind the effect to props. You're seeing the console. But while refresh the page, api calling twice. Even though App. Accordingly, for some reason, react seems to call new App() (or whatever is similar to this in react framework) twice and I have no idea what to search for. IO version: 4. next. Taking out either of the 2 lines of code in the render results in an error, where only the text of the navbar shows up (but only shows up once, not twice), and is not clickable. GET_CATS would set the loading state in the redux store to true, that way you can interrogate it in the respective componentDidMount() functions and only make the call to the api when loading is false. I am rendering a simple react app component but I am not able to understand why "Inside useeffect hook. 5, you can also see grayed out duplicate render log if you have installed React dev tools & it will confirm that its done by React strict mode I am rendering a class component Rates within the functional component of App. Here's the thing, on the first render, classes is fully populated and ready to go. This is the expected behavior. The Title component is a simple functional component, and I'm not sure why this is happening. log so you can see it in action) out of the constructor and into the componentDidMount At the start of my App. When i console. js 12. So it does, but twice, the sending function works just fine, but the app itself gets rendered twice, thus it sends the data twice. I am using node`s express framework. The thing is that componentDidMount is being called twice, the first one with undefined JWT and the second For React Hooks in React 18, this means a useEffect() with zero dependencies will be executed twice. The code is thus querying the same data twice, which should be avoided. This is my This is my very simple React app. you need to use AbortController, to abort the request after the component unmounted on the return This can get messy. Modified 11 months ago. This is because connect is a higher order component. That way, combined with a couple state variables (useState), you can ensure that you are only prompting the user one set of times and it'll stay in memory as long as the component is mounted. In that mode, react quickly mounts and unmounts every component to stress-test the app and to simulate quick user interaction. Modified 4 years, 5 months ago. When your <DC /> component changes state, it passes the new state value count to the component Joker. getElementById('root')); Please follow the link to get a detailed idea about React. count() function to count the number of times the App component renders. My react app uses axios for POST-requests to the server. 2) and Before opening a new issue, please take a moment to review our community guidelines to make the contribution process easy and effective for everyone involved. You need to clean up requests or events when the component unmounted. Here are the most likely causes: 1. it intentionally double render components (only in development) to enforce you, not use side effects on some of your component's lifecycle events. For example, when a user tabs away from a screen and back, React should be able to immediately show the previous screen. The other thing I wanted to address is that you should make things like that fun When I use console. log output twice because you're doing updateState twice. log displays twice, once with the previous value and another with the new change. StrictMode> tag in the index. render( <React. ) Events firing twice inside axios interceptor (Read this thinking maybe I managed to integrate my react app with Okta authentication and it works. js // this will render everything twice in dev env <React. . This was by design, but it was annoying and misleading to see console. Solution: If you ever need to keep Strict Mode in your component but need to make your useEffect no render twice, you could use useRef : The most common reason for seeing an API call twice in a React application is React’s Strict Mode. This means that React will skip rendering the component, and reuse the last rendered result. I created a brand new project from create-react-app, it only one component other than App component so it is not so complex and complicated but still the problem persists. Hi @obouchta and @floweb,. So what happens is: component mounts, fetches; component unmounts. const WalletVerification = React. The component renders twice, even in production build. I am pretty new to React so apologies if this is a dumb question, which I suspect it is. Code: Check index. SOLUTION. count changes;. React can "render" your component, e. The issue i am facing is that the container component loads twice. Also, axios sends out an HTTP request, which is handled asynchronously. Expected behavior These are the logs with Strict mode ON, React 18 & latest Next. The component is fetching data from a API and then sends the data to a stateless component via props. js. log exected twice? I don't understand why this is happening - I have an app that increments and decrements a counter when the buttons are pressed to display an increasing list of easter egg brands from a collection. StrictMode>. It can take a few reloads to get the fresh content because the service worker, which is persisting in the browser between You appear to have some confusion about what your logs mean. 0. Viewed 501 times 0 I created a had this issue as well and it had to do with StrictMode being enabled which gets added by default when you create a new React app. So if you update a state, it will render twice if what you're rendering is affected by that state. I'm calling API inside useEffect. I tried the solutions on the internet, but I couldn't. log executes with [] setCurrentData(result); // Causes second rerender and I have routs with children and on the first load, everything working fine but once I'm staring through the site, the components starting to render twice. Provide details and share your research! But avoid . StrictMode> tag in index. The trick is using componentWillUpdate, although the example is using apollo client, and not fetch the solutions is equivalent. log once. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company If you check React Dev Tools of what is being rendered you'll see something like connect(App) as well as App by itself, so your console. Hi, sorry just another quick question to the second comment, you said: "Calling setData changes App's state, which triggers a re-render. This is done to detect problems with purity. StrictMode> closing tag from your index. – React StrictMode calls all Effects twice to make sure their cleanup/unmount handlers work as intended. I did a tutorial on Scrimba (it's a website with an in-browser IDE) that had this code as one of the exercises. If you would like to render it only when the data is available you could do something like {Object. js import { createRoot } from 'r You render once with prevMonthStamp being undefined. 3. In my react app I'm trying to use Hooks, createContext, useContext, useState and UseState for the first time and for some reason the app looks like it loads my header hook twice. /App. log("test"); console. 2 Socket. log to test my app, it logs the data two times here an screenshot and the code. js In my App component, I simply console log "Hello from APP". jsx and remove StrictMode around the rendering of App, you will see it will only console. 0 (which is different versioning from react-scripts). Just so you know, if you have strict mode enabled in your react app, it will always render twice on the first render. My problem is that I have a simple app using latest ReactJs (v 18. If you're using create-react-app, the problem is that there is a service worker that is likely caching the page for offline use. At this point the component will rerender, accounting for the first change. The states like iValue, pValue, The navbar keeps appearing twice at the top and bottom of the page. 👍 8 MargaretKrutikova, joshmadewell, KaviSharma, gabrieldelisle, hellriser4, triforcely, pratikt-cuelogic, and RamonBalthazar reacted with thumbs up emoji I'd like to add that, that's why is better to have class-components for this use-cases rather than function-components. My question is, why is it rendering twice? Below is App. I went backwards and deleted code until it stopped happening and for whatever reason it starts when I use the state hook: I started new React project via the command: npx create-react-app my-app --template typescript Then, I changed the App component to look like that: import * as React from 'react'; export default This is an example from the Google AdSense application page. How to fix when a component renders twice in react. I think there was only one render. Thanks for your feedback, I tried looking into this issue but cannot seems to be able to reproduce it. For an useEffect to trigger twice, if you for example make a timer, if you forget the cleanup function, the timer will increment 2 times as fast, warning you that you forgot to cancel it. H Skip to main content. I have read that it may be because of mistakes in code so I deleted all the things which caused "compiled with warnings", but even though now terminal This causes react apps to render twice. When the page is loaded, the componentDidMount function is being called twice. Change the order to see the expected behaviour you're looking for. log. Stack Overflow like fetching something from the api on loading the page, It's intended to make React render twice in development mode so that it can give you suggestions on how you can improve your React component renderes twice (useeffect runs twice) Hot Network Questions Is it a good idea to immerse the circuit in an engineered fluid in order to minimize circuit drift I got your problem. I have a very simplified React app (v18. 8. js: import {Outlet} from "react-. But the problem is I have to press the submit button twice to see the log. I have an App in reactjs, it should send some data to my back-end Strapi server. I can do that but for some reason, in the UI I’m getting alert displayed 2x. For all i know, i am doing everything right here. It only happens in development mode and should help to find accidental side effects in the render phase. however in Production environment, it only The reason why this happens is an intentional feature of the React. 2. And it's my app which shows up twice. Its just rerendering with updated state or props. StrictNode which is wrapped arround App component. The function is: async function WAIT(time: any) { await new Promise((r) => setTimeout(r, time)) } export async function In my reactjs project, component is rendered twice. s: Don't forget to import useEffect from react before using it. The cause of the issue is in the development of react 18 with strict mode, the useEffect will be mounted-> unmounted-> mounted, which call the API twice. I am trying to develop a phaser3 application with React. js fixed the double mount problem for all of my components. but the problem is, my form is getting submitted twice, and creating duplicate records with same values. These functions are: Class component constructor, render, and shouldComponentUpdate methods Class component static getDerivedStateFromProps When using React. 0 I have server working with ExpressJS, but I don't understand why is react client side, connecting to server twice with my custom hook. js, in I am studying ReactJs and faced some issues. On the first load the data is empty and on the second load the data is there. I am not using strict mode. 0, React-Router v4, React 16 (Fiber) The answer selected use old React Router v3. 0 back in 2018 and in 16. Following is the index. js from <React. All components of the page renders in the first <body> once more: <html lang="en"&g For rendering twice, the advance is that you see if you forgot to make a clone of an array before pushing something to it, as it will show an certain item twice. call the function, as many times as it needs to in order to compute what needs to be committed to the Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company React 18 renders your component twice in development mode. I have an app component and test component. Effects firing twice in <React. Calling a function form of setState will defer evaluation (this can be dangerous when the setState call is event dependent and the event has Notice how every time you hover over the StoryTray component, “Create Story” gets added to the list again. log('app') " in the callback npm run start checkout the conso Your useEffect only fires once. If remove, rendred once. Then when the state changes from 0 -> 1 there is another render. 1 week repeats from a month to another, so when you change the month, 2 Weeks components end with the same key prop. Each item added to the list also has a delete button associated with it. I I have to render the navbar twice in order for it to work, but it shows up twice, where only the second navbar is functional. In my case, I developed some UI components as a package, and inside that I have an example folder with the React app which Create React App. // index. First render with the user state being null -> useEffect dispatchs the user data retrieved from local storage -> user state gets updated -> another render since you are listening to the state change. The render function should also be a pure function, meaning there are no side-effects, like console logging. From the official docs, emphasis mine: "useRef returns a mutable ref object whose . Once without the data and once with the data In React. [HMR] Waiting for update signal from WDS Hello from APP [WDS] Hot Module Replacement enabled. It will increase your else if condition approach. StrictMode> <App /> </React. There are many similar question but nothing could help for me. js function App() {useEffect(() => Is your App wrapped with React. I have a simple React app with a dropdown, button and list. change : ReactDOM. if I remove the componentDidMount, the problem is fixed. js application, you might encounter a behavior where the useEffect function runs twice during the initial render in development mode. App. count() function runs twice, which I interpret as App having rendered twice on startup. Js, The strict Mode is enabled. Here is a custom hook that can be used instead of useEffect(), with zero dependencies, that will give the old (pre React React: content loading twice. You shouldn't change any variables that were created before your component. For API requests. When using the useState hook, it re-renders whenever a state value changes, not necessarily every time you call setState (which was the old behaviour). This feature will give React apps better performance out-of-the-box, but requires components to be resilient to effects being mounted and destroyed multiple times. You will find a single render. I created a new React app from scratch and integrated the latest versions of keycloak-js (v11. The reason you see two console logs is because, the first time RecipeList is called with no data (empty object), and the second time when the data becomes available. js code -> const root = ReactDOM. I am completely new to that so I have no idea what and where could go wrong. " is being printed on console twice. 04 Node. Let's find out if there is a way to There are a few common reasons why a simple React component might render twice. The second render returns the same classes object, with no differences --> thus the second re-render is unneeded and The fetch is async await, then setState. However, the popup, allowing to chose with which app he wants to continue the process, appears. This answer the correct way to fix OP's problem, and I upvoted, but the last line is wrong. When a user opens the android app, an auth0 login page opens in the browser and upon successful signing in, it redirects the user back to the app. Every time StoryTray renders, it adds “Create Story” again at the end of the same array. So working with two apps at once isn't possible (like the library's example page and also the consumer app). OS: Ubuntu 19. I don't know why is the reason for this behaviour, but I mostly ask because I'm worried that the component could be rendered twice due to some mistake and eventually the app could be overloaded due to bad coding. This is the way that reactjs tell you to double check your API result or other functionality is working properly or not. Ask Question Asked 4 years, 5 months ago. I understand why, because state changes from its initial value of empty array to an array of objects, causing a render. js v12. StrictMode> ); console. React version: 17. Thanks. js I am studying the react lifecycle and and watched some tutorials but when I made my app i noticed my app is Mounting twice. Strict mode is enabled by default if you created the app using create-react-app, like so: const root = ReactDOM. Then you render again, now with prevMonthStamp equal to some number. StrictMode>, rootElement ); According to react docs:. Asking for help, clarification, or responding to other answers. Strict mode can’t automatically This is related to strict effects in react 18, which means you'll only see this behaviour if you use <StrictMode>, and only during development. StrictMode which is what causes your code to run in strict mode and in strict mode the consoles are shown twice because each function is made to run twice in development mode. Every Axios request is firing twice in my react redux node app. g. I am having some issues when loading a container component. Reference Code Splitting; First Contentful Paint; Conclusion Structuring components in an optimized way and using React APIs effectively will increase the performance of large-scale apps. I think this is a fairly common way of doing it. That's all. Using the react profiler Chrome Extension I can see that the App component is loaded once on initial render and that the RouterProvider component is loaded once on render then once again when "hook 1" It's happening because in your app in strict mode. App This is caused by the re-rendering of components, React renders each components multiple time, Call console. clicking Back button in your app would always show a spinner instead of cached data—an easy way to detect apps that call fetch + setState directly in their effects. Observe terminal output. I would also note that if your render method has more conditions. React StrictMode is a development tool intended for producing hints about potential issues in React applications. Here is my App. And it worked fine in that environment. Should it not just be printed once after the component is rendered, since there is no state change and the dependency array is I want to have "ans" logged in console as soon as I click on the submit button. StrictMode and also Detecting unexpected side effects Using: Apollo Client 2. This is deliberate and part of the React Strict Mode features, which is automatically enabled in Next. Strict mode can’t automatically detect side effects for you, but it can help you spot them by You signed in with another tab or window. log present in useEffect gets printed twice when we load the application for the first time. The output is as follows: [HMR] Waiting for update signal from WDS Hello from APP [WDS] Hot Module Replacement enabled. You are console logging as an unintentional side-effect in the App component's return statement, so any "expected behavior" should be thrown out the window. But when I imported it into VS code and ran it In the future, we’d like to add a feature that allows React to add and remove sections of the UI while preserving state. useEffect(() => { console. To resolve your issue you just need to unwrap your App. When I am starting a react app by "npm start" command in VScode terminal, it starts to loading forever on the browser. setDefaultLanguage() (and your console. Npm You signed in with another tab or window. log the componentdidmount, didupdate and willunmount i noticed my app 1st mounts then unmounts and mounts again My app only contains the file we get from npx create-react-app with a h1 tag Locked This is a basic 30 line app . Is it supposed to To do this, I am using both useState hook and useEffect hook. While in <StrictMode/>, react will detect unexpected side effects which will call lifecycle functions more than once duration the development mode, will not be trigger twice in production. You signed in with another tab or window. Meaning that function is going to get called on every render. How to call loading function with React useEffect only once. createRoot(document. 2+ and higher, see instructions for older npm versions) Need help with React Router 6. Or you can try to use this hook : useLayoutEffect I made a simple Async function and wanted to test run it in my react app. This happens is an intentional feature of the React. Removing the offending component from index. StrictMode ?If so, it's okay that your component rendered twice. For Next. StrictMode> //app. Improve this question. First render as we expect and other render is for react strict mode. log('Load Once') }, []); It trigger twice while page refresh manually, it will trigger once if navigate from another page. you’ll be able to avoid double API calls in your React app and improve the overall Describe the bug The create-react-app config is loading twice, but should not be. You are having this problem because of how you are setting the key prop of the Week component on the renderWeeks function. js from the create-react-app. I put a console. js:. StrictMode /> was added in React 18. The loading screen is displayed before the main page is shown. 405. You may need to change your effects accordingly, even if they have an empty dependency list and would normally not unmount before the site is closed. Game. getElementById('root')); root. After adding rewrites to next. js In my component Constructor and render method are called twice. js, the console. You can test this by giving a hardcoded value to gameId where it should only call useEffect once: <GameInner gameId={"5"} /> // hardcoded id variable Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company I am developing a react native app with Auth0 support. The fetch function call is in useEffect. This is what's happening right now: setIsLoaded(true); // Causes 1st rerender and so console. StrictMode cannot spot side-effects at once, but it can help us find them by intentionally invoking twice some key functions. In I've got a simple react app that has a Login that receives a Json Web Token on successful authentication and the passes it to a sibling component (Members) that in its componentDidMount uses this JWT to make a fetch call to the server. The intention of the code was to add it once at the end. You signed out in another tab or window. You have to store the results to a variable which gets rendered in your component. It show me result below . If I take login page example then If you want to run it every time it re-renders, you need to remove the second parameter of the useEffect function, the , [] part. Related questions. Description the default render functio My component was triggering twice. Service workers were enabled by default until CRA v2. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company This is because of how React functions. Libraries are one-to-many (one library installed in many apps), but this associates a library with only one app by linking that app's react folder to the library. Rendering twice will only appear in the development environment and StrictMode has many benefits for development:. Then you create a brand new randomFunc which you pass to Hello, causing a re-render there, where the useEffect notices randomFunc changed, causing the effect to retrigger. I'm just making a simple recipe fetching app using the create-react-app setup, but when I tried logging the response it logged it twice. Here is App. log inside of useEffect hook and pass the searchText vaiable inside the useEffect dependency array. The anchor tag has hash url and after clicking the page is rendering only one time but analytics showing two page loads. root. memo for a performance boost in some cases by memoizing the result. current property is initialized to the passed argument (initialValue). log will be called twice. however in Production environment, it only renders once. There are a few common reasons why a simple React component might render twice. log(searchText); ; }, [searchText]); P. However, I'm facing the following problem: React Hooks: useEffect() is called twice even if an empty array is used as an argument. js is invoked only once in index. This will prevent React from re-rendering components unnecessarily and will stop methods from being The component renders twice, even in production build. If the component was really rendered once, why the console. It's because React renders components 2 times in the development environment. I put console inside. When using React's Strict Mode, components can render twice in development mode to help identify potential issues. This is because strict mode in react is used to find out common bugs in component level and to do so, react renders twice a single component. The second render was success but the side effect is my child component's that using context value from its parent as an initialState (using useState hooks) set its initial state to empty array. I am not sure how to achieve the same effect with React because if I render the loading screen as a React component, it will not be displayed while the page is loading as it needs to wait for the DOM to be rendered first. js: import '. Am I missing something glaring? To be clear I have read the following posts and NONE are an answer to my question: Every axios request firing twice in react-redux app? (I am not using Cross Origin. While that is a quick fix your not addressing the bigger problem, react promotes composes the ui and your code is more of an anti-pattern. StrictMode> React. log(‘Tab1 called’) just before the return statement, it will produce a double output of “Tab1 called” in the console when visiting /tab1. js for the below code <React. Below is If React Strict mode is causing your function to fire twice there are a few solutions: Remove Strict mode entirely. Because of Strict mode - React will render twice. I can see that app console is only rendered once but the test component Now we have reduced the React app initial load time by 70% with a few tweaks by using code splitting effectively in the dashboard component. The issue is when I install the package into an example app using npm i . If you go to Index. 4+. This is to make sure that there are no side effects. Following the React AJAX example i have created a JSX file which purpose is to fetch and render a movie. I'm developing a NEXT JS project and can't find a solution for a twice rendering app! Problem. I don't like to do this, but its the easiest solution When developing an application in React 18+, you may encounter an issue where the useEffect hook is being run twice on mount. Service Workers. When I inspect the page the elements show that App appears twice and duplicates the nav. I'm not too far into the implementation and have it pretty bear bones and not refactored (and not great coding practices). I create a react project using create react app and try to call the api once then printing result to the console.
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