use-effect

问题 This question already has answers here : Does React batch state update functions when using hooks? (3 answers) Closed 9 months ago . Actually I am not getting the right point of this problem. So seeking help. I have this state full functional component. The thing I have noticed here is that when I fetch data using useEffect hook then I get the response properly. The problem is, when I execute console.log("ok") in the return statement it provides output multiple times in the console. The

问题 This question already has answers here : Does React batch state update functions when using hooks? (3 answers) Closed 9 months ago . Actually I am not getting the right point of this problem. So seeking help. I have this state full functional component. The thing I have noticed here is that when I fetch data using useEffect hook then I get the response properly. The problem is, when I execute console.log("ok") in the return statement it provides output multiple times in the console. The

问题 I am trying to make an API call in a functional component which is a react-hook and based on the result, re-render the component's content. Here is the code: Component which is calling the API- function IntegrationDownshift() { render( <Paper square> {setResults(inputValue).map( (suggestion, index) => renderSuggestion({ suggestion, index, itemProps: getItemProps({ item: suggestion.userFullName }), highlightedIndex, selectedItem }) )} </Paper> ); } Here is the setResults function: function

问题 I am following this: Merge two JSON data into one with particular key values Now, I added an useEffect() hook. How can I make use of useRef to store my result? This is an asynchronous function. const App = (props) =>{ let result = useRef () useEffect(()=>{ return()=> (result.current = [courtdata, balldata].reduce((p, q) => p.map((c, i) => Object.assign({}, {[c.court_id] : q[i].color})))) }.[someTrigger]) return( <ul> {result.current.map(r => ( <li> Court id - {r.court_id} | Ball colour - {r

问题 I am following this: Merge two JSON data into one with particular key values Now, I added an useEffect() hook. How can I make use of useRef to store my result? This is an asynchronous function. const App = (props) =>{ let result = useRef () useEffect(()=>{ return()=> (result.current = [courtdata, balldata].reduce((p, q) => p.map((c, i) => Object.assign({}, {[c.court_id] : q[i].color})))) }.[someTrigger]) return( <ul> {result.current.map(r => ( <li> Court id - {r.court_id} | Ball colour - {r

问题 I don't understand why my useEffect() React function can't access my Component's state variable. I'm trying to create a log when a user abandons creating a listing in our app and navigates to another page. I'm using the useEffect() return method of replicating the componentWillUnmount() lifecycle method. Can you help? Code Sample let[progress, setProgress] = React.useState(0) ... user starts building their listing, causing progress to increment ... console.log(`progress outside useEffect: $

问题 In the useEffect function, If i just mention the getResults function variable, the app doesn't crash, but when i call it as i'm doing in code below, i get these errors : react-dom.development.js:21857 Uncaught TypeError: destroy is not a function and Consider adding an error boundary to your tree to customize error handling behavior. function App() { const [foods, setFoods] = useState([]); const [isLoaded, setIsLoaded] = useState(false); useEffect(() => getResponse()); const getResponse =

问题 In the useEffect function, If i just mention the getResults function variable, the app doesn't crash, but when i call it as i'm doing in code below, i get these errors : react-dom.development.js:21857 Uncaught TypeError: destroy is not a function and Consider adding an error boundary to your tree to customize error handling behavior. function App() { const [foods, setFoods] = useState([]); const [isLoaded, setIsLoaded] = useState(false); useEffect(() => getResponse()); const getResponse =

问题 I've been learning React and I read that the function returned from useEffect is meant to do cleanup and React performs the cleanup when the component unmounts. So I experimented with it a bit but found in the following example that the function was called every time the component re-renders as opposed to only the time it got unmounted from the DOM, i.e. it console.log("unmount"); every time the component re-renders. Why is that? function Something({ setShow }) { const [array, setArray] =

问题 I am using a regEx expression to filter out the youtube ID of a youtube link. I am using it in two different spots - It works great in the first spot... but the second time I use the same expresion, with the same input, it does not work. Here are the two functions. First - Here is the one that works. The user inputs the data in a text input, and it returns match[2], which is the youtube ID at the end of the link. The user can copy paste in a whole paragraph of text containing a youtube link,