Timms Mastering JavaScript Design Patterns

Discover how to use JavaScript design patterns to create powerful applications with reliable and maintainable code
1. Auflage 2025
ISBN: 978-1-78398-799-3
Verlag: De Gruyter
Format: PDF
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 290 Seiten

If you are a developer interested in creating easily maintainable applications that can grow and change with your needs, then this book is for you. Some experience with JavaScript (not necessarily with entire applications written in JavaScript) is required to follow the examples written in the book.

Autoren/Hrsg.

Timms, Simon

Fachgebiete

• Mathematik | Informatik EDV | Informatik Programmierung | Softwareentwicklung Software Engineering

Leseproben

Chapter 1. Designing for Fun and Profit

JavaScript is an evolving language that has come a long way from its inception. Possibly more than any other programming language, it has grown and changed with the growth of the World Wide Web. The exploration of how JavaScript can be written using good design principles is the topic of this book. The preface of this book contains a detailed explanation of the sections of the book.

In the first half of this chapter, we'll explore the history of JavaScript and how it came to be the important language that it is today. As JavaScript has evolved and grown in importance, the need to apply rigorous methods to its construction has also grown. Design patterns can be a very useful tool to assist in developing maintainable code. The second half of the chapter will be dedicated to the theory of design patterns. Finally, we'll look briefly at antipatterns.

The topics covered in this chapter are:

• The history of JavaScript
• What is a design pattern?
• Antipatterns

The road to JavaScript

We'll never know how language first came into being. Did it slowly evolve from a series of grunts and guttural sounds made during grooming rituals? Perhaps it developed to allow mothers and their offsprings to communicate. Both of these are theories, all but impossible to prove. Nobody was around to observe our ancestors during that important period. In fact, the general lack of empirical evidence lead the Linguistic Society of Paris to ban further discussions on the topic, seeing it as unsuitable for serious study.

The early days

Fortunately, programming languages have developed in recent history and we've been able to watch them grow and change. JavaScript has one of the more interesting histories in modern programming languages. During what must have been an absolutely frantic 10 days in May of 1995, a programmer at Netscape wrote the foundation for what would grow up to be modern JavaScript.

At that time, Netscape was involved in the first of the browser wars with Microsoft. The vision for Netscape was far grander than simply developing a browser. They wanted to create an entire distributed operating system making use of Sun Microsystems' recently released Java programming language. Java was a much more modern alternative to C++ that Microsoft was pushing. However, Netscape didn't have an answer to Visual Basic. Visual Basic was an easier to use programming language, which was targeted at developers with less experience. It avoided some of the difficulties around memory management which makes C and C++ notoriously difficult to program. Visual Basic also avoided strict typing and overall allowed more leeway.

Brendan Eich was tasked with developing Netscape repartee to VB. The project was initially codenamed Mocha but was renamed LiveScript before Netscape 2.0 beta was released. By the time the full release was available, Mocha/LiveScript had been renamed JavaScript to tie it into the Java applet integration. Java applets were small applications that ran on the browser. They had a different security model from the browser itself and so were limited in how they could interact with both the browser and the local system. It is quite rare to see applets these days, as much of their functionality has become part of the browser. Java was riding a popular wave at that time and any relationship to it was played up.

The name has caused much confusion over the years. JavaScript is a very different language from Java. JavaScript is an interpreted language with loose typing that runs primarily on the browser. Java is a language that is compiled to bytecode, which is then executed on the Java Virtual Machine. It has applicability in numerous scenarios from the browser (through the use of Java applets) to the server (Tomcat, JBoss, and so on) to full desktop applications (Eclipse, OpenOffice). In most laypeople's minds, the confusion remains.

JavaScript turned out to be really quite useful for interacting with the web browser. It was not long until Microsoft had also adopted JavaScript in their Internet Explorer to complement VBScript. The Microsoft implementation was known as JScript.

By late 1996, it was clear that JavaScript was going to be the winning web language for the near future. In order to limit the amount of language deviation between implementations, Sun and Netscape began working with the European Computer Manufacturers Association (ECMA) to develop a standard to which future versions of JavaScript would need to comply. The standard was released very quickly (very quickly in terms of how rapidly standard organizations move) in July of 1997. On the off chance that you have not seen enough names yet for JavaScript, the standard version was called ECMAScript, a name which still persists in some circles.

Unfortunately, the standard only specified the very core parts of JavaScript. With the browser wars raging, it was apparent that any vendor that stuck with only the basic implementation of JavaScript would quickly be left behind. At the same time, there was much work going on to establish a standard document object model (DOM) for browsers. The DOM was, in effect, an API for a web page that could be manipulated using JavaScript.

For many years, every JavaScript script would start by attempting to determine the browser on which it was running. This would dictate how to address elements in the DOM, as there were dramatic deviations between each browser. The spaghetti of code that was required to perform simple actions was legendary. I remember reading a year-long 20 part series on developing Dynamic HTML (DHTML) drop-down menus such that they would work on both Internet Explorer and Netscape Navigator. The same functionality can now be achieved with pure CSS without even having to resort to JavaScript.

Note

DHTML was a popular term in the late 1990s and early 2000s. It really referred to any web page that had some sort of dynamic content that was executed on the client side. It has fallen out of use as the popularity of JavaScript has made almost every page a dynamic one.

Fortunately, the efforts to standardize JavaScript continued behind the scenes. Versions 2 and 3 of ECMAScript were released in 1998 and 1999. It looked like there might finally be some agreement between the various parties interested in JavaScript. Work began in early 2000 on ECMAScript 4, which was to be a major new release.

A pause

Then, disaster struck! The various groups involved in the ECMAScript effort had major disagreements about the direction JavaScript was to take. Microsoft seemed to have lost interest in the standardization effort. It was somewhat understandable as it was around that time that Netscape self-destructed and Internet Explorer became the de facto standard. Microsoft implemented parts of ECMAScript 4 but not all of it. Others implemented more fully featured support but, without the market leader on board, developers didn't bother using them.

Years passed without consensus and without a new release of ECMAScript. However, as frequently happens, the evolution of the Internet could not be stopped by a lack of agreement between major players. Libraries such as jQuery, Prototype, Dojo, and MooTools papered over the major differences in browsers, making cross-browser development far easier. At the same time, the amount of JavaScript used in applications increased dramatically.

The way of Gmail

The turning point was, perhaps, the release of Google's Gmail application in 2004. Although XMLHttpRequest, the technology behind Asynchronous JavaScript and XML (AJAX), had been around for about 5 years when Gmail was released, it had not been well used. When Gmail was released, I was totally knocked off my feet by how smooth it was. We've grown used to applications that avoid full reloads, but at that time it was a revolution. To make applications like that work, a great deal of JavaScript is needed.

Note

AJAX is a method by which small chunks of data are retrieved from the server by a client instead of refreshing the entire page. The technology allows for more interactive pages that avoid the jolt of full page reloads.

The popularity of Gmail was the trigger for a change that had been brewing for a while. Increasing JavaScript acceptance and standardization pushed us past the tipping point for the acceptance of JavaScript as a proper language. Up until that point, much of the use of JavaScript was for performing minor changes to the page and for validating form input. I joke with people that in the early days of JavaScript the only function name that was used was .

Applications such as Gmail that have a heavy reliance on AJAX and avoid full-page reloads are known as single page applications (SPAs). By minimizing the changes to the page contents, users have a more fluid experience. By transferring only JavaScript Object Notation (JSON) payload, instead of HTML, the amount of bandwidth required is also minimized. This makes applications appear to be...

Über Autor(innen)

Timms Simon :

Simon Timms is a developer who works in the oil and gas industry in Calgary, Alberta. He has a BSc in Computing Science from the University of Alberta and a Masters from Athabasca University. He is interested in distributed systems, visualization, and the acquisition of ice-cream. This is his first book, but he blogs frequently on diverse topics such as code contracts and cloud computing at blog.simontimms.com. He is involved in the local.NET and JavaScript community, and speaks frequently at conferences. Contacted by Shweta Pant on 28-8-2017 for the third edition of Mastering JavaScript Design Patterns book