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
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17
Index

Basic functions

We have been calling functions for a while already. Remember prompt(), console.log(), push(), and sort() for arrays? These are all functions. Functions are a group of statements, variable declarations, loops, and so on that are bundled together. Calling a function means an entire group of statements will get executed.

First, we are going to have a look at how we can invoke functions, and then we will see how to write functions of our own.

Invoking functions

We can recognize functions by the parentheses at the end. We can invoke functions like this:

nameOfTheFunction();
functionThatTakesInput("the input", 5, true);

This is invoking a function called nameOfTheFunction with no arguments, and a function called functionThatTakesInput with three required arguments. Let's have a look at what functions can look like when we start writing them.

Writing functions

Writing a function can be done using the function keyword. Here...