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Asynchronous JavaScript
Asynchronous JavaScript allows you to perform tasks without freezing the execution of other code. It uses callbacks, promises, and async/await to handle asynchronous operations.
What is Asynchronous in JavaScript?
In JavaScript, asynchronous refers to the ability to execute tasks without freezing the execution of other code. Asynchronous operations allow you to handle time-consuming tasks such as making network requests or accessing databases without freezing the entire program.
Asynchronous JavaScript vs Synchronous
Asynchronous JavaScript allows code to continue executing while waiting for certain operations to complete, improving responsiveness. In contrast, synchronous JavaScript blocks the execution of other code until an operation is complete, potentially causing delays.
Where is Asynchronous JavaScript Used?
Asynchronous JavaScript is used in various scenarios, including:
- Fetching data from APIs
- Performing file I/O operations
- Handling user interactions and events
Asynchronous JavaScript Example
function fetchData() {
return new Promise((resolve, reject) => {
setTimeout(() => {
const data = 'Example data';
resolve(data);
}, 5000);
});
}
async function displayData() {
const result = await fetchData();
console.log(result);
}
// Open Developer Tools Console. The Example data should be displayed after 5 seconds.
displayData();This example uses the fetchData() function, which returns a promise that resolves after a delay of 5000 milliseconds. The displayData() function uses await to wait for the promise to resolve and then logs the result.
Asynchronous JavaScript Interview Questions
- What is asynchronous programming in JavaScript?
- How do callbacks work in asynchronous JavaScript?
- What are promises and how do they handle asynchronous operations?
- What are the different ways to handle errors in asynchronous JavaScript?
- How do you use asynchronous JavaScript to improve the performance of your code?
- What are some of the challenges of writing asynchronous JavaScript?
FAQ (Interview Questions and Answers)
-
What is asynchronous programming in JavaScript?
Asynchronous programming in JavaScript allows tasks to be performed without freezing the execution of other code.
Asynchronous programming in JavaScript ensures that tasks are executed in order, one after the other.
Asynchronous programming in JavaScript is not supported by modern browsers.
-
How do callbacks work in asynchronous JavaScript?
Callbacks in asynchronous JavaScript are only used for error handling purposes.
Callbacks in asynchronous JavaScript are deprecated and should be avoided.
Callbacks in asynchronous JavaScript are functions that are passed as arguments to be executed after a certain task is complete.
-
What are promises and how do they handle asynchronous operations?
Promises in asynchronous JavaScript are used for synchronous operations.
Promises in asynchronous JavaScript represent the eventual completion or failure of an asynchronous operation and allow you to handle the result usingthen()andcatch()methods.
Promises in asynchronous JavaScript are limited to handling only simple operations.
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