Science Knowings: JavaScript Course For Social Media

Promise Chaining

Promise Chaining

Welcome back! In this session, we're diving into the world of Promise Chaining, a technique to handle asynchronous operations in JavaScript.

The Concept of Promise Chaining

Promise chaining allows you to connect multiple asynchronous operations sequentially, ensuring that the output of one operation becomes the input for the next.

Why Use Promise Chaining?

Benefits of Promise Chaining:

  • Improved code readability and flow
  • Error handling becomes more manageable
  • Easier to handle complex asynchronous workflows

How to Implement Promise Chaining

.then() method:

fetch('data.json')
  .then(response => response.json())
  .then(data => console.log(data))

Chaining Multiple Promises

You can chain multiple promises to execute tasks in a sequence:

fetch('data1.json')
  .then(response1 => response1.json())
  .then(data1 => {
    return fetch('data2.json')
  })
  .then(response2 => response2.json())
  .then(data2 => console.log(data1, data2))

Example of Promise Chaining

Suppose we have two APIs:

  • API 1: Get user details (/users/:id)
  • API 2: Get user posts (/users/:id/posts)
fetch(`/users/${userId}`) // Get user details
  .then(response => response.json())
  .then(user => fetch(`/users/${user.id}/posts`)) // Get user posts
  .then(response => response.json())
  .then(posts => console.log(user, posts))

async/await syntax

async/await provides a cleaner and more concise way to write asynchronous code:

async function getUserAndPosts() {
  const user = await fetch(`/users/${userId}`).then(r => r.json());
  const posts = await fetch(`/users/${user.id}/posts`).then(r => r.json());

  console.log(user, posts);
}

Advantages of using async/await

Benefits of async/await:

  • Makes asynchronous code look like synchronous code
  • Improves code readability and maintainability

Promise Chaining in Real-World Applications

Promise chaining finds applications in:

  • Handling user authentication and authorization
  • Fetching and processing data from multiple sources
  • Performing complex data transformations and manipulations

Next topic: Error Handling in Promises

In the next session, we'll cover Error Handling in Promises. Follow us to learn how to handle errors effectively in asynchronous code!