Book Image

JavaScript from Beginner to Professional

By : Laurence Lars Svekis, Maaike van Putten, Codestars By Rob Percival
4 (5)
Book Image

JavaScript from Beginner to Professional

4 (5)
By: Laurence Lars Svekis, Maaike van Putten, Codestars By Rob Percival

Overview of this book

This book demonstrates the capabilities of JavaScript for web application development by combining theoretical learning with code exercises and fun projects that you can challenge yourself with. The guiding principle of the book is to show how straightforward JavaScript techniques can be used to make web apps ranging from dynamic websites to simple browser-based games. JavaScript from Beginner to Professional focuses on key programming concepts and Document Object Model manipulations that are used to solve common problems in professional web applications. These include data validation, manipulating the appearance of web pages, working with asynchronous and concurrent code. The book uses project-based learning to provide context for the theoretical components in a series of code examples that can be used as modules of an application, such as input validators, games, and simple animations. This will be supplemented with a brief crash course on HTML and CSS to illustrate how JavaScript components fit into a complete web application. As you learn the concepts, you can try them in your own editor or browser console to get a solid understanding of how they work and what they do. By the end of this JavaScript book, you will feel confident writing core JavaScript code and be equipped to progress to more advanced libraries, frameworks, and environments such as React, Angular, and Node.js.
Table of Contents (19 chapters)
16
Other Books You May Enjoy
17
Index

async and await

We have just seen the Promise syntax. With the async keyword, we can make a function return a Promise. This makes the Promises nicer to read and look a lot like synchronous (non-concurrent) code. We can use this Promise just like we learned in the previous section, or we can use the more powerful await keyword to wait until the Promise is done. await only works in an asynchronous function.

In an asynchronous context, we can await other Promises as well, as can be seen in this example:

function saySomething(x) {
    return new Promise(resolve => {
        setTimeout(() => {
            resolve("something" + x);
        }, 2000);
    });
}
async function talk(x) {
    const words = await saySomething(x);
    console.log(words);
}
talk(2);
talk(4);
talk(8);

Can you figure out what this code does? We call the asynchronous function talk() three times in a row with no break. Each of these function calls is awaiting the saySomething() function...