⏳ Mastering JavaScript Event Loop and Concurrency Model! ⏳
Understanding the JavaScript event loop and concurrency model is essential for building responsive and efficient web applications. From asynchronous operations to task scheduling, mastering these concepts unlocks the full potential of JavaScript.
I’ve compiled a series of exercises designed to deepen your understanding of the event loop and concurrency model:
– Explore the order of execution for asynchronous operations using promises and async/await.
– Learn how to handle errors, perform parallel operations, and schedule tasks with setTimeout, setImmediate, and Promise.all.
– Dive into the nuances of microtasks and macrotasks, and gain insights into the inner workings of the event loop.
Why delve into the event loop and concurrency model?
– They empower you to write scalable and responsive code, enhancing user experience.
– Understanding these concepts is crucial for debugging performance issues and optimizing code.
– Mastery of the event loop and concurrency model sets you apart as a proficient JavaScript developer, ready to tackle complex challenges.
Let’s unravel the mysteries of the event loop and concurrency model together! Share your insights, solutions, or questions, and let’s elevate our JavaScript skills together.
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Dive deep into JavaScript’s event loop and concurrency model and unleash the full potential of your web applications! 🌐💡✨
Exercise 1: Understanding Asynchronous Execution
Problem: Write JavaScript code that logs “Start” first, then “Middle” after 2 seconds, and finally “End” after 4 seconds.
Explanation: Demonstrates how asynchronous functions are queued and executed in the event loop.
Code:
console.log(“Start”);
setTimeout(() => {
console.log(“Middle”);
}, 2000);
setTimeout(() => {
console.log(“End”);
}, 4000);
Exercise 2: Order of Execution with Promises
Problem: Write JavaScript code that logs the numbers 1, 2, and 3 in order using promises.
Explanation: Illustrates how promises are resolved asynchronously, affecting the order of execution.
Code:
Promise.resolve().then(() => console.log(1));
Promise.resolve().then(() => console.log(2));
Promise.resolve().then(() => console.log(3));
Exercise 3: Event Loop Execution Order
Problem: Write JavaScript code that logs “A” first, then “B” after a microtask, and finally “C” after a macrotask.
Explanation: Clarifies the order of execution between microtasks and macrotasks in the event loop.
Code:
console.log(“A”);
Promise.resolve().then(() => console.log(“B”));
setTimeout(() => {
console.log(“C”);
}, 0);
Exercise 4: Nested Asynchronous Operations
Problem: Write JavaScript code that performs two asynchronous operations sequentially: fetching user data and then fetching their posts.
Explanation: Demonstrates handling sequential asynchronous operations using promises.
Code:
const getUserData = () => {
return new Promise(resolve => {
setTimeout(() => {
resolve({ id: 1, name: “Alice” });
}, 1000);
});
};
const getUserPosts = userId => {
return new Promise(resolve => {
setTimeout(() => {
resolve([“Post 1”, “Post 2”, “Post 3”]);
}, 1000);
});
};
getUserData()
.then(user => getUserPosts(user.id))
.then(posts => console.log(posts));
Exercise 5: Handling Errors in Promises
Problem: Write JavaScript code that handles errors in a promise chain.
Explanation: Shows how to handle errors using the catch method in promise chains.
Code:
Promise.resolve()
.then(() => {
throw new Error(“Oops!”);
})
.catch(error => console.error(error.message));
Exercise 6: Parallel Asynchronous Operations
Problem: Write JavaScript code that performs multiple asynchronous operations in parallel and waits for all of them to complete.
Explanation: Demonstrates how to use Promise.all to execute multiple promises concurrently.
Code:
const promises = [
Promise.resolve(“Result 1”),
Promise.resolve(“Result 2”),
Promise.resolve(“Result 3”)
];
Promise.all(promises)
.then(results => console.log(results));
Exercise 7: Event Loop with setTimeout
Problem: Write JavaScript code that logs numbers from 1 to 5 with a delay of 1 second between each log.
Explanation: Illustrates how to use recursive setTimeout calls to create a delay in the event loop.
Code:
const logNumbers = (num, max) => {
console.log(num);
if (num < max) {
setTimeout(() => logNumbers(num + 1, max), 1000);
}
};
logNumbers(1, 5);
Exercise 8: Using setImmediate
Problem: Write JavaScript code that demonstrates the behavior of setImmediate compared to setTimeout.
Explanation: Shows how setImmediate differs from setTimeout in the event loop execution order.
Code:
console.log(“Start”);
setImmediate(() => console.log(“Immediate”));
setTimeout(() => console.log(“Timeout”), 0);
console.log(“End”);
Exercise 9: Concurrent HTTP Requests
Problem: Write JavaScript code that makes multiple HTTP requests concurrently and processes their responses.
Explanation: Demonstrates concurrent execution of asynchronous tasks using promises and async/await.
Code:
const fetchData = async () => {
const [userData, postData] = await Promise.all([
fetch(‘https://jsonplaceholder.typicode.com/users’).then(response => response.json()),
fetch(‘https://jsonplaceholder.typicode.com/posts’).then(response => response.json())
]);
console.log(userData);
console.log(postData);
};
fetchData();
Exercise 10: Scheduling Tasks with setImmediate
Problem: Write JavaScript code that schedules a task using setImmediate and observes its behavior.
Explanation: Illustrates how setImmediate schedules a task to execute immediately after the current event loop cycle.
Code:
setImmediate(() => console.log(“Immediate task”));
console.log(“End of script”);
