JavaScript Promises

Advanced

Approx. 3 weeks

Assumes 6hrs/wk (work at your own pace)

Join thousands of students Course Summary

Learn how to handle asynchronous work with ease! In this course, you'll use Native JavaScript Promises to write asynchronous code that is easy to read, easy to write and easy to debug.

Along the way, you'll be using Promises to make a webapp come to life!

Why Take This Course?

Every web developer needs to be able to work with asynchronous code. Network requests, browser events, web workers and just about every else about the web happens asynchronously.

JavaScript developers normally rely on callbacks to execute async code, but Native JavaScript Promises offer a much easier solution. With Promises, error handling is streamlined and it becomes possible to flexibly chain lots of asynchronous work without creating a tangled mess of callbacks.

Prerequisites and Requirements

We expect that students have built web apps in the past and they are familiar with the pitfalls of callback-heavy code. There is no HTML or CSS in this class.

JavaScript Skills Required:

• Using functions to return objects and other functions
• Basic understanding of scope and closures
• Reading and writing named and anonymous callbacks
• Array methods like .forEach and .map

Other Requirements:

• Ability to use GitHub to clone repos and checkout branches
• Comfort with command line tools

See the Technology Requirements for using Udacity.

What Will I Learn? Projects Project 2: Public Transportation App You will build an application that allows users to select a departure and arrival train station, and see a list of trains, times, and durations. A default train schedule will be provided that should be used when the application is offline. If a network connection exists, the application will query an endpoint that provides information about all arrival and departure times. Syllabus Lesson 1 - Creating Promises

• Why Promises?
• Promises syntax and scope
• Simplifying common, useful methods with Promises
• Basic error handling

Lesson 2 - Chaining Promises

• Creating sequences of async work manually
• Advanced error handling
• Techniques for generating sequences of async work with array methods

Project

Throughout the course (mostly in the second lesson), you'll be using Promises to load data into the Exoplanet Explorer app, which was designed to help people learn a little bit about planets around other stars.