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Design patterns are reusable solutions to commonly occurring problems in software design.
They are both exciting and a fascinating topic to explore in any programming language. One reason for this is that they help us build upon the combined experience of many developers that came before us and ensure we structure our code in an optimized way, meeting the needs of problems we’re attempting to solve.
Design patterns also provide us a common vocabulary to describe solutions. This can be significantly simpler than describing syntax and semantics when we’re attempting to convey a way of structuring a solution in code form to others.
If you find yourself needing to read further about these topics, a list of suggested titles is provided for convenience. If you would like to learn how to write beautiful, structured and organized code, I believe this is pattterns book for you.
I will always be grateful for the talented technical reviewers who helped review and improve this book, including those from the community at large. The knowledge and enthusiasm they brought to the project was simply amazing. The official technical reviewers tweets and blogs are also a regular source of both ideas and inspiration and I wholeheartedly recommend checking them out. I would also like to thank Rebecca Murphey http: Finally, I would stfanov to thank my wonderful wife Ellie, for all of her support pattfrns I was putting together this publication.
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Should you wish to learn more about the language, I am happy to recommend the following titles:. 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 stoyxn skip to the chapter ” What is a Pattern? Design patterns can be traced back to the early work of an architect named Christopher Alexander. Srefanov 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 in a sgefanov 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 called Design Patterns: 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 twenty-three core Object-Oriented design patterns frequently used around the world today.
Another way of looking at patterns are as templates for how we solve problems – ones which can be used in quite a few different situations. So, why is it important to understand patterns and be familiar with them?
Design patterns have three main benefits:. Patterns are not an exact solution. To understand how useful patterns can be, let’s review a very simple element selection problem that the jQuery library solves for us. Imagine that we have a script where for each DOM element found on a page with class “foo” we wish to increment a counter. What’s the most efficient way to query for this collection of elements?
Well, there are a few different ways this problem could be tackled:.
Select all of the elements in the page and then store references to them. Next, filter this collection and use regular expressions or another means to only store those with the class “foo”.
Use a modern native browser feature such as querySelectorAll to select all of the elements with the class “foo”. Use a native feature such as getElementsByClassName to similarly get back the desired collection. So, which of these options is the fastest? It’s actually option 3. In a real-world application however, 3. Developers using jQuery don’t have to worry about this problem however, as it’s luckily abstracted away for us using the Facade pattern.
As we’ll review in more detail later, this pattern provides a simple set of abstracted interfaces e. As we’ve seen, this means less time having to be concerned about implementation level details.
Behind the scenes, the library simply opts for the most optimal approach to selecting elements depending on what patterbs current browser supports and we just consume the abstraction layer. Although we know that querySelectorAll patters to solve this problem, compare the effort involved in using jQuery’s Facade interfaces vs. Abstractions using patterns can offer real-world value. Remember that not every algorithm, best practice or solution represents what might be considered a complete pattern.
There may be a few key ingredients here that are missing and the pattern community is generally wary of something claiming to be jagascript unless it has been heavily vetted.
Even if something is presented to us which appears to meet the criteria for a pattern, it should not be stefanog one until it has undergone suitable periods of scrutiny and testing sstefanov others.
Looking back upon the work by Alexander once more, he claims that a pattern should both be a process and a “thing”. This definition is obtuse on purpose as he follows by saying that it is the process which should create the “thing”.
This is a reason why patterns generally focus on addressing a visually identifiable structure i. In studying design patterns, it’s not irregular to come across the term “proto-pattern”. Well, a javascrit that has not yet been known to pass the “pattern”-ity tests is pahterns referred to as a proto-pattern. Proto-patterns may result from the work of someone that has established a particular solution that is worthy of sharing with the community, but may not have yet had the opportunity to have been vetted heavily due to its very young age.
Alternatively, the individual s sharing the pattern may not have the time or interest of going through the “pattern”-ity process pafterns might release a short description of their proto-pattern instead. Brief descriptions or snippets of this type of pattern are known as sttefanov. The work involved in fully documenting a qualified pattern can be quite daunting. Looking back at some of the earliest ajvascript in the field of design patterns, a pattern may be considered “good” if it does the following:.
We would be forgiven for thinking that a proto-pattern which fails to meet guidelines isn’t worth learning from, however, this is far from the truth. Many proto-patterns are actually quite good. One of the additional requirements for a pattern to be valid is that they display some recurring phenomenon.
This is often something that can be qualified in at least three key areas, referred to as javascgipt rule of three. To show recurrence using this rule, one must demonstrate:. You may be curious about how a pattern author might approach outlining structure, implementation and purpose of a new pattern.
A pattern stefajov initially presented in the form of a rule that establishes a relationship between:. A design pattern should have a:. Design patterns are quite a powerful approach to getting all of the developers in an organization or team on the same page when creating or maintaining solutions.
If considering working on a pattern of your own, remember that although they may have a heavy initial cost in the planning and write-up phases, the value returned from that investment can be quite worth it. Always research thoroughly before working on new patterns however, as you may find it more beneficial to use or build on top of existing proven patterns than starting afresh. Although this book is aimed at those new to design patterns, a fundamental understanding of how a design pattern is written javawcript offer a number of useful benefits.
Stotan starters, we can gain a deeper appreciation pattenrs the reasoning behind why a pattern is needed. We can also learn how to tell if a pattern or proto-pattern is up to scratch when reviewing it for our own needs. Writing good patterns is a challenging task. Patterns not only need to ideally provide a substantial quantity of reference material for end-users, but sstefanov also need to be able to defend why they are necessary.
Having read the previous section on what a pattern is, we may think that this in itself is enough to help us identify patterns we see in the wild. This is actually not completely true. It’s not always clear if a piece of code we’re looking at is following a set pattern or just accidentally happens to appear like it does. When we’re looking at a body of javascriph we think may be using a pattern, we should consider writing down some of the aspects of the code that we believe falls under a particular existing pattern or set of patterns.
In many cases of pattern-analysis we can find that we’re just looking at code that stoyab good principles and design practices that could happen to overlap with the rules for a pattern by accident.
Remember – solutions in which neither interactions nor defined rules appear are not patterns.
If patterbs in venturing down the path of writing your own design patterns I recommend learning from patterne who have already been through the process and done it well.
Explore structure and semantics – this can be done by examining the interactions and context of the patterns you are interested in so you can identify the principles that assist in organizing those patterns together in useful configurations. Once we’ve exposed ourselves to a wealth of stefanof on pattern literature, we may wish to begin writing our pattern using an existing format and see if we can brainstorm new ideas for improving it or integrating our ideas in there.
An example of a developer that did this is in recent years is Christian Heilmann, who took the existing Module pattern and made some fundamentally useful changes to it to create the Revealing Module pattern this is one of the patterns covered later in this book.