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Learning JavaScript Design Patterns by Addy Osmani

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Chapter 1. Introduction

One of the most important aspects of writing maintainable code is being able to notice the recurring themes in that code and optimize them. This is an area where knowledge of design patterns can prove invaluable.

In the first part of this book, we will explore the history and importance of design patterns, which can really be applied to any programming language. If you’re already sold on or are familiar with this history, feel free to skip to Chapter 2 to continue reading.

Design patterns can be traced back to the early work of an architect named Christopher Alexander. He would often write publications about his experience in solving design issues and how they related to buildings and towns. One day, it occurred to Alexander that when used time and time again, certain design constructs lead to a desired optimal effect.

In collaboration with Sara Ishikawa and Murray Silverstein, Alexander produced a pattern language that would help empower anyone wishing to design and build at any scale. This was published back in 1977 in a paper titled “A Pattern Language,” which was later released as a complete hardcover book.

Some 30 years ago, software engineers began to incorporate the principles Alexander had written about into the first documentation about design patterns, which was to be a guide for novice developers looking to improve their coding skills. It’s important to note that the concepts behind design patterns have actually been around in the programming industry since its inception, albeit in a less formalized form.

One of the first and arguably most iconic formal works published on design patterns in software engineering was a book in 1995 called Design Patterns: Elements of Reusable Object-Oriented Software. This was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides—a group that became known as the Gang of Four (or GoF for short).

The GoF’s publication is considered quite instrumental to pushing the concept of design patterns further in our field, as it describes a number of development techniques and pitfalls, as well as providing 23 core object-oriented design patterns frequently used around the world today. We will be covering these patterns in more detail in Chapter 7.

In this book, we will take a look at a number of popular JavaScript design patterns and explore why certain patterns may be more suitable for your projects than others. Remember that patterns can be applied not just to vanilla JavaScript (i.e., standard JavaScript code), but also to abstracted libraries such as jQuery and Dojo. Before we begin, let’s look at the exact definition of a “pattern” in software design.

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