Promises
Promises were introduced to address the callback hell issue and provide a more structured way of handling asynchronous code. A Promise is an object representing the eventual completion or failure of an asynchronous operation.
Promises provide a more structured way to handle asynchronous code and simplify error handling. They can be chained using .then() and .catch().
Example: Here, fetchUserDataWithPromise returns a Promise, simulating the asynchronous nature of an API request. The .then() method handles the resolved value, and the .catch() method handles errors.
Javascript
// Function to fetch user data with a Promisefunction fetchUserDataWithPromise() { // Simulating an API request const userData = { id: 1, name: "John Doe" }; return new Promise((resolve, reject) => { if (userData) { resolve(userData); } else { reject("Error fetching user data."); } });}// Using the PromisefetchUserDataWithPromise() .then((data) => { console.log("Processing user data:", data); console.log("User data processed successfully."); }) .catch((error) => { console.error("Error:", error); }); |
Output
Processing user data: { id: 1, name: 'John Doe' }
User data processed successfully.
Callbacks vs Promises vs Async/Await
Callbacks, Promises, and Async/Await are three different approaches in JavaScript for handling asynchronous operations. Let’s briefly discuss each.
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