The JavaScript Workshop

A New, Interactive Approach to Learning JavaScript

Joseph Labrecque, Jahred Love, Daniel Rosenbaum, Nick Turner, Gaurav Mehla, Alonzo L. Hosford, Florian Sloot, Philip Kirkbride

• Éditeur: Packt Publishing
• Année: 2019
• ISBN:
  9781838645885
• Édition: 1
• Sujet: Informatique
• Sous-sujet: Programmation Open Source

Get to grips with the fundamentals of JavaScript and learn to build the programming skills that will kickstart your career as a software developer

Key Features

• Learn the basics of JavaScript programming to create dynamic web pages
• Explore the fundamentals of back-end development using Node.js
• Tackle challenging development problems and apply solutions to real-world situations

Book Description

If you're looking for a programming language to develop flexible and efficient apps, JavaScript is a great choice. However, while offering real benefits, the complexity of the entire JavaScript ecosystem can be overwhelming. This Workshop is a smarter way to learn JavaScript. It is specifically designed to cut through the noise and help build your JavaScript skills from scratch, while sparking your interest with engaging activities and clear explanations.

Starting with explanations of JavaScript's fundamental programming concepts, this book will introduce the key tools, libraries and frameworks that programmers use in everyday development. You will then move on and see how to handle data, control the flow of information in an application, and create custom events. You'll explore the differences between client-side and server-side JavaScript, and expand your knowledge further by studying the different JavaScript development paradigms, including object-oriented and functional programming.

By the end of this JavaScript book, you'll have the confidence and skills to tackle real-world JavaScript development problems that reflect the emerging requirements of the modern web.

What you will learn

• Write clean, maintainable and eloquent JavaScript code
• Build websites using plain JS and various frameworks and libraries
• Simplify your workflow with package managers such as Gulp and Grunt
• Use Node.js to build server-side JavaScript applications
• Improve the functionality of your applications with browser APIs
• Implement asynchronous programming to build apps that can multitask

Who this book is for

The JavaScript Workshop is the ideal guide to JavaScript for beginners. It is designed for anyone who wants to get started learning JavaScript. Whether you're an aspiring web developer, or are just curious about learning how to code with a versatile programming language, this book will help you get up and running. Previous development experience is not required, but basic prior knowledge of HTML and CSS will help you get the most from this book.

1. Getting to Know JavaScript

Overview

By the end of this chapter, you will be able to locate JavaScript elements along with other code elements in a web browser; identify different versions of JavaScript supported by various web browsers; construct simple JavaScript commands; discuss the range of modern approaches to JavaScript; describe JavaScript's capabilities and create an alert box popup in a web browser.

This chapter describes the foundational background of JavaScript so that we can move forward and achieve competency with this widely used programming language.

Introduction

JavaScript is a language with interesting beginnings. In its early days, it was not taken very seriously—the only widely accepted, functionally correct use for the language was to perform client-side validation of form data. Many developers only copied and pasted simple code snippets that performed a single action on a website they were building. All these code snippets did were very simple actions such as reveal an alert to the user or provide a date countdown—simple logic.

Today, JavaScript is a whole different beast—and one with the power to literally build out entire HTML documents, revise CSS styling on the fly, and securely transport and interpret data from various remote sources. Whereas in times past, HTML was the primary technology on the web, in the present era, JavaScript is king.

Any introduction to JavaScript requires a foundational background of the history and origins of the language in order to move forward and achieve competency. This chapter introduces us to JavaScript, from its history to modern implementations. It also provides us with additional information on various uses of the language so that we can provide a proper context for what comes next.

What Is JavaScript and How Is It Used?

JavaScript is a weakly-typed, multi-paradigm, event-driven, object-oriented programming language. It includes the ability to work with strings, dates, arrays, objects, and more. It is generally used on the client-side within web browser environments but can also be used in other environments such as servers and desktop applications. The runtime environment is very important for JavaScript—especially since it, by itself, does not include any networking, file, graphics, or storage capabilities on its own.

JavaScript versus Other Languages

If you are approaching JavaScript with experience in other languages such as Java or Python, things might seem a bit odd. While many languages (such as Java) must be compiled to run, JavaScript is run exactly as-is and does not require this additional step.

Though the language is used within many environments and for many purposes, JavaScript is fundamentally one of the three languages that are native to the web. The other two languages are the HTML semantic markup language and the CSS styling and layout language. All three are very different from one another in purpose and function, but they are all meant to work together in a single environment. Let's go over them:

• Hypertext Markup Language (HTML): This is the most fundamental of these three languages as it defines the elements that compose an HTML page and defines the flow of basic information that's presented to the user.
• Cascading Style Sheets (CSS): This is used to define a set of stylistic layout rules, which adds visual flourish and advanced layout to defined HTML elements.
• JavaScript(JS): This works to enable interactivity in web pages and is what will be the focus of this book.

With all three of these languages, there is a basic understanding of the separation of concerns, that is, HTML provides the content and structure, CSS provides the styling and layout, and JavaScript provides the interactivity. While this understanding still holds sway, many frameworks do not exactly abide by this separation and mix these various languages together in some shape or form. Some developers are okay with this, while others are not. It's definitely an issue to be aware of when getting into this field, but it is ultimately up to you which stance you take, based on your particular needs. In my opinion, there is no hard and fast answer to a question like this.

Exercise 1.01: Languages Discovery

Let's go ahead and examine a website to see whether we can spot how HTML, JavaScript, and CSS are all represented. You can choose any website you like for this exercise.

Note

All the examples and screenshots in this book will use Google Chrome as the web browser of choice. You can use the browser you prefer, though some of the steps that are shown may differ between various browsers.

Let's get started:

1. Within your web browser, enter a URL in the address bar and press Enter/Return to load the chosen resource. For this example, let's use https://packt.live/2oXOE67—the Angular website. Of course, you can choose any website that you'd like to explore.
2. Now, right-click anywhere within the browser viewport to summon a contextual menu. Select the option that allows you to view the source code of the page. In Chrome, this is labeled View Page Source.
3. The source code for the page will then appear in a new tab. You can examine how the page is structured and pick out the various HTML, CSS, and JavaScript elements from the bare source code:
   
   Figure 1.1: Much can be learned from examining the bare source code
4. With the source code exposed, scroll down and identify the various HTML elements within the page structure. You'll likely find a <head> tag and a <body> tag (which are mandatory), along with various <p> and <h1> to <h6> tags within the page.
   Here is an example of some basic HTML content (not actually from the Angular website):
   <body>
   <h1>Welcome!</h1>
   <p>Angular is a framework used to build web applications.</p>
   <p>Create high-performing and accessible applications using Angular.</p>
   </body>
5. Now, try and locate either embedded CSS rules within a <style> element, or even a linked CSS file. Here is an example of some embedded CSS:
   <style>
   color: red;
   margin-top: 40px;
   position: relative;
   text-align center;
   </style>
   And here is a linked CSS file:
   <link rel="stylesheet"href="styles.css">
6. Finally, we'll locate some JavaScript. Much like CSS, JavaScript can be found embedded within a page using the <script> tag, or entire JavaScript files can be linked though a similar mechanism. Here, we are locating some embedded JavaScript:
   <script>
   function writeMessage() {
   document.getElementById("message").innerHTML = "Hello From JavaScript!";
   }
   </script>
   Here is a linked JavaScript file:
   <script src="main.js"></script>
   Choosing to view the source code of public web pages like this was once a common way to learn about web technologies.
   Note
   In various websites and examples, you may see a type attribute included with the <script> tag specifying type="text/javascript". In HTML5, this is not necessary and is the default attribute. If you must target previous versions of HTML, you will need to specify it.

So far, we have introduced the JavaScript programming language and examined its primary runtime environment (the web browser). We also had a brief look at JavaScript's relationship to HTML and CSS as one of the three native web technologies.

In the next section, we'll take a look at the history of JavaScript and how it has evolved over the years.

A Brief History of the JavaScript Language

We've seen how JavaScript is often integrated within a web environment, but how did this language come about? We need to go back to the early 1990s and understand what the web looked like in those days before we begin talking about JavaScript itself.

The story really begins with Netscape and the web browser they created named Netscape Navigator. This new browser was based on the successful Mosaic web browser with the intent to commercialize it. During that time, and depending on...