JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

In this course we will learn how to use the ES2017 async and await keywords to write asynchronous code that is more readable and easier to follow than equivalent code based on long promise chains or deeply nested callbacks. 

The await operator takes a promise and then pauses the function execution until that promise is settled which allows for an async function to read like sequential synchronous code.

This course will start by showing us how to convert a function doing a simple HTTP request into an async function using async/await. By the end of the course we will be able to loop over asynchronous data sources using a `for-await-of` async generator function.

This lesson introduces the ES2017 `async` and `await` keywords. It shows how to write a short asynchronous function that makes an HTTP request and parses the response.

Write an Asynchronous Function with async/await

In this lesson, we’re exploring how asynchronous functions can be seamlessly called within a promise chain — just like any other function that returns a promise.

Call an Asynchronous Function in a Promise Chain

Any function can be made asynchronous, including function expressions, arrow functions, and methods. This lesson shows the syntax for each of the function types.

Convert Any Function into an Asynchronous Function

This lesson shows how regular control flow statements such as `try`/`catch` blocks can be used to properly handle errors in asynchronous functions. Oftentimes, the resulting code is easier to read than complex promise chains with `.catch()` methods.

Handle Errors in Asynchronous Functions

You can await multiple promises either sequentially or concurrently, depending on where you put the `await` operators. This lesson shows both approaches and compares the performance characteristics.

Await Multiple Promises Sequentially or Concurrently

Oftentimes, you want to kick off multiple promises in parallel rather than awaiting them in sequence. This lesson explains how that can be achieved in a readable manner using `await`, the `Promise.all()` method, and destructuring assignment.

Await Multiple Promises Concurrently with Promise.all()

The `await` operator is not restricted to ES2015 promises. It can be used to await any *thenable* — that is, any object with a `.then()` method. This lesson illustrates how to await promises that have been created using a promise library.

Use the await Operator with Any Thenable

We finish the course by looking at asynchronous iterators, a generic data access protocol for asynchronous data sources. This asynchronous iteration scheme is built on top of a new `for`-`await`-`of` loop and async generator functions.

Asynchronous JavaScript with async/await

Marius Schulz

Course Content