Week 3

In this session, you'll learn how to write asynchronous code that is both efficient and easy to understand. We'll explore Promises and the async/await syntax, which allow you to handle long-running operations—such as network requests—without blocking the user interface. Mastering these techniques is key to building responsive applications that deliver a smooth user experience.

Contents

• Preparation

• Session Plan (for mentors)

• Assignment

Session Learning Goals

By the end of this session, you will be able to:

• Use Promises to run asynchronous code.

  • Understand the anatomy of a Promise and how to use it

  • Using .then() to add callback behaviour

  • Using .catch() to handle errors

  • Chaining multiple .then()

• Use async and await to make your code more readable

  • Defining async functions

  • Using await when calling async functions

  • Error handling using await

// Example: Using promise with .then()
let user1;
fetch("https://jsonplaceholder.typicode.com/users/1")
  .then((response) => (user1 = response.json()))
  .then(() => console.log("User 1:", user1))
  .catch(() => (user1 = null));

// Example: Using promise with async/await
async function getUser() {
  try {
    const response = await fetch(
      "https://jsonplaceholder.typicode.com/users/2",
    );
    const user = await response.json();
    return user;
  } catch (error) {
    return null;
  }
}