Introduction

Brief Explanation of the Tutorial's Goal

In this tutorial, we aim to introduce you to the basics of asynchronous programming. Asynchronous programming is a technique that is often used in web development to improve the performance of applications.

What the User Will Learn

Upon completing this tutorial, you should have an understanding of:

• What asynchronous programming is
• Why it is important and beneficial
• How to use JavaScript's async/await

Prerequisites

To get the most out of this tutorial, you should have a basic understanding of JavaScript.

Step-by-Step Guide

Understanding Asynchronous Programming

Asynchronous programming is a means of parallel programming in which a unit of work runs separately from the main application thread. When the work is complete, it notifies the main thread about its completion or failure so the main thread can pick up where it left off. This technique can help to improve the performance of your application.

Using JavaScript's async/await

The async function declaration defines an asynchronous function, which returns an AsyncFunction object. The await keyword is used to pause async function execution until a Promise is fulfilled or rejected, and to resume execution of the async function after fulfillment.

Code Examples

Async Function Example

async function myFunction() {
  // You can await a Promise here
  const result = await someAsyncCall();
  // After the await keyword, the function execution pauses until the promise is resolved, then it resumes
  console.log(result);
  // After the promise is resolved, the rest of the code can use the result as if it was synchronous
}

myFunction();

In the above code snippet, myFunction is an asynchronous function. Inside this function, we are making an asynchronous call someAsyncCall(). The await keyword before this call ensures that JavaScript waits until that promise settles and returns its result.

Handling Errors in async/await

async function myFunction() {
  try {
    const result = await someAsyncCall();
    console.log(result);
  } catch (error) {
    console.log('An error occurred: ' + error);
  }
}

myFunction();

In this example, we've added a try/catch block to handle any errors that might occur during the execution of the someAsyncCall() function.

Summary

In this tutorial, we learned what asynchronous programming is and how it can improve the performance of our applications. We also learned how to use JavaScript's async/await to write cleaner and more readable asynchronous code.

The next step would be to dive deeper into Promise and async/await, and learn about other advanced topics like handling multiple promises at the same time.

Practice Exercises

1. Write an async function that waits for 1 second before it logs 'Hello, World!'. Hint: You can use setTimeout.

2. Write an async function that makes a fetch request to an API and logs the response. Make sure to handle errors correctly.

Solutions

1. Solution to the first exercise:

async function delayedGreeting() {
  await new Promise(resolve => setTimeout(resolve, 1000));
  console.log('Hello, World!');
}

delayedGreeting();

Here, we create a new Promise that resolves after 1 second (1000 milliseconds). We then await this promise, which means that the function execution will pause for 1 second before logging 'Hello, World!'.

1. Solution to the second exercise:

async function fetchAPI() {
  try {
    const response = await fetch('https://api.example.com');
    const data = await response.json();
    console.log(data);
  } catch (error) {
    console.log('An error occurred: ' + error);
  }
}

fetchAPI();

In this example, we make a fetch request to 'https://api.example.com'. We then convert the response to JSON and log it. If an error occurs during any of these steps, it will be caught and logged.