In the previous chapter, we covered many of the new and powerful features released in ES6. We discussed the evolution of JavaScript and highlighted the key additions in ES6. We discussed scope rules, variable declaration, arrow functions, template literals, enhanced object properties, destructuring assignment, classes and modules, transpiling, and iterators and generators.
In this chapter, we will learn what an asynchronous programming language is and how to write and understand asynchronous code. In the first topic, we will define asynchronous programming and show how JavaScript is an asynchronous, event driven programming language. Then, we will outline callbacks and show how to use callbacks to write asynchronous JavaScript. We will then define promises and demonstrate how to use promises to write asynchronous JavaScript. In the final topic, we will present the async/await syntax and simplify our asynchronous code using promises and this syntax.