Menu
How I can skip first run in useEffect hook.
useEffect(() => { const first = // ??? if (first) { // skip } else { // run main code } }, [id]); 
814
We can make the React useEffect callback not run on the first render by creating a ref that keeps track of whether the first render is done. Then we can check the ref's value to see when the first render is done and run the function we want when the first render is done.
To prevent this from happening, we need a variable that can be set to false after the initial render. We can then use this variable to prevent the side effect from taking place during the initial render.
If you have just made a new project using Create React App or updated to React version 18, you will notice that the useEffect hook is called twice in development mode. This is the case whether you used Create React App or upgraded to React version 18.
Side Effect Runs Only Once After Initial Render You do not want to make this API call again. You can pass an empty array as the second argument to the useEffect hook to tackle this use case. useEffect(() => { // Side Effect }, []); In this case, the side effect runs only once after the initial render of the component.
The useRef hook can be used to store any mutable value, so you could store a boolean indicating if it's the first time the effect is being run. Not the answer you're looking for? Browse other questions tagged reactjs react-hooks or ask your own question.
We use the useEffect () hook to simulate componentDidMount and componentDidUpdate, but it seems like useEffect () is being ran after every render, even the first time. The way to check if it's the first time for useEffect function is being run in React Hooks - Anna…
Want the #1 way to learn React? Become a React pro in 30 minutes a day with the React Bootcamp. Why is it called useEffect? When the core React Hooks were added to the library in 2018 (useState, useEffect, and so on), many developers were confused by the name of this hook: "useEffect".
The first effect is the main one as if you were using it in your component. It will run, discover that isMounted isn't true and will just skip doing anything. Then after the bottom useEffect is run, it will change the isMounted to true - thus when the component is forced into a re-render. It will allow the first useEffect to render normally.
The useRef hook can be used to store any mutable value, so you could store a boolean indicating if it's the first time the effect is being run.
Example
const { useState, useRef, useEffect } = React; function MyComponent() { const [count, setCount] = useState(0); const isFirstRun = useRef(true); useEffect (() => { if (isFirstRun.current) { isFirstRun.current = false; return; } console.log("Effect was run"); }); return ( <div> <p>Clicked {count} times</p> <button onClick={() => { setCount(count + 1); }} > Click Me </button> </div> ); } ReactDOM.render( <MyComponent/>, document.getElementById("app") );<script src="https://unpkg.com/[email protected]/umd/react.development.js"></script> <script src="https://unpkg.com/[email protected]/umd/react-dom.development.js"></script> <div id="app"></div>If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
