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In JavaScript, exporting a variable from a callback depends on whether the callback is synchronous or asynchronous. For asynchronous operations, you cannot directly return the value; instead, you must use callbacks, Promises, or async/await.
Using a Callback Function
If the operation is asynchronous, pass another function to handle the result when it’s ready.
function getData(callback) {setTimeout(() => {const result = "Hello from callback";callback(result);}, 1000);}getData((data) => {console.log(data); // "Hello from callback"});प्रतिलिपी केली!✕प्रतिलिपी कराTip: This is the traditional approach but can lead to callback hell if nested deeply.
Using Promises
Promises provide a cleaner way to handle asynchronous results and allow chaining.
function getData() {return new Promise((resolve) => {setTimeout(() => {resolve("Hello from Promise");}, 1000);});}getData().then((data) => {console.log(data); // "Hello from Promise"});प्रतिलिपी केली!✕प्रतिलिपी कराTip: Promises make error handling easier with .catch().
Using Async/Await
javascript - How to get returned a value by a callback function - Stack ...
6 जाने, 2013 · You can return whatever you like from the function and use that as normal, but as that happens before the callback you don't have access to the result from the asynchronous call at that time.
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