Mastering JavaScript Basics for Interview Success: Day 57
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Chapter 1: Interview Preparation Insights
Welcome to Day 57 of our 100-day journey dedicated to mastering JavaScript, where we delve into crucial concepts to prepare for coding interviews. Today, we will focus on a significant topic: the functionality and application of Promise.allSettled().
Understanding Promise.allSettled()
When working with multiple promises in JavaScript—tasks that may take time to complete, such as retrieving data from an API—Promise.allSettled() becomes an invaluable asset. This method allows us to wait for all promises to resolve, regardless of their success or failure.
JavaScript Definition
The Promise.allSettled() method takes an iterable of promises and returns a single promise. This returned promise fulfills when all input promises settle, producing an array of objects that detail the outcome of each promise.
Syntax
Promise.allSettled(iterable)
Parameters
- iterable: An iterable, like an array, containing promises.
Return Value
- A promise that resolves when all promises in the iterable have settled, or immediately if the iterable is empty.
For more details, please refer to the [Getting Started with a Simple Example](#).
Use Case
Consider a scenario where users can subscribe to a newsletter. The signup process involves several asynchronous tasks, such as:
- Sending a confirmation email.
- Updating the database with the subscriber's information.
- Logging the event and redirecting the user to the homepage.
Implementing Promise.allSettled()
Step 1: Create three promises for sending emails, updating the database, and logging the event. Here's an example of how this could look:
function sendConfirmationEmail(email) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(Confirmation email sent to ${email});}, 1000);
});
}
function updateDatabase(userInfo) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(Database updated with ${userInfo});}, 1500);
});
}
function logEventWithRedirect(eventInfo, redirectURL) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(Event logged and redirecting: ${eventInfo});}, 2000);
});
}
Step 2: Create a user signup function utilizing Promise.allSettled().
async function userSignup(email, userInfo) {
const results = await Promise.allSettled([
sendConfirmationEmail(email),
updateDatabase(userInfo),
logEventWithRedirect(Signed up with email ${email}, '/dashboard'),
]);
results.forEach(result => {
if (result.status === 'fulfilled') {
console.log('Task succeeded:', result.value);} else {
console.error('Task failed:', result.reason);}
});
}
Step 3: Invoke the user signup function.
const userEmail = '[email protected]';
const userInformation = { name: 'Tuffy', age: 23 };
userSignup(userEmail, userInformation);
Conclusion
Promise.allSettled() is essential in handling multiple asynchronous tasks effectively, allowing us to manage both successful and failed outcomes seamlessly. Stay tuned for tomorrow's discussion on comparing Promise.any(), Promise.allSettled(), Promise.race(), and Promise.all() through simple examples.
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Chapter 2: Video Resources
To further enhance your understanding, check out these helpful videos:
Mastering JavaScript - Everything You Need To Know. This comprehensive video covers essential JavaScript concepts crucial for mastering the language.
JavaScript Mastery Complete Course. A thorough tutorial for beginners to advanced users, covering all aspects of JavaScript you need to know.