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TypeScript Design Patterns
TypeScript Design Patterns

TypeScript Design Patterns: Boost your development efficiency by learning about design patterns in TypeScript

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TypeScript Design Patterns

Chapter 2. The Challenge of Increasing Complexity

The essence of a program is the combination of possible branches and automated selections based on certain conditions. When we write a program, we define what's going on in a branch, and under what condition this branch will be executed.

The number of branches usually grows quickly during the evolution of a project, as well as the number of conditions that determine whether a branch will be executed or not.

This is dangerous for human beings, who have limited brain capacities.

In this chapter, we are going to implement a data synchronizing service. Starting by implementing some very basic features, we'll keep adding stuff and see how things go.

The following topics will be covered:

  • Designing a multi-device synchronizing strategy
  • Useful JavaScript and TypeScript techniques and hints that are related, including objects as maps and the string literal type
  • How the Strategy Pattern helps in a project

Implementing the basics

Before we start to write actual code, we need to define what this synchronizing strategy will be like. To keep the implementation from unnecessary distractions, the client will communicate with the server directly through function calls instead of using HTTP requests or Sockets. Also, we'll use in-memory storage, namely variables, to store data on both client and server sides.

Because we are not separating the client and server into two actual applications, and we are not actually using backend technologies, it does not require much Node.js experience to follow this chapter.

However, please keep in mind that even though we are omitting network and database requests, we hope the core logic of the final implementation could be applied to a real environment without being modified too much. So, when it comes to performance concerns, we still need to assume limited network resources, especially for data passing through the server and client, although the implementation...

Growing features

What we've done so far is basically useless. But, from now on, we will start to add features and make it capable of fitting in practical needs, including the capability of synchronizing multiple data items with multiple clients, and merging conflicts.

Synchronizing multiple items

Ideally, the data we need to synchronize will have a lot of items contained. Directly changing the type of data to an array would work if there were only very limited number of these items.

Simply replacing data type with an array

Now let's change the type of the data property of DataStore and DataSyncingInfo interfaces to string[]. With the help of TypeScript, you will get errors for unmatched types this change would cause. Fix them by annotating the correct types.

But obviously, this is far from an efficient solution.

Server-centered synchronization

If the data store contains a lot of data, the ideal approach would be only updating items that are not up-to-date.

For example, we can create a...

Getting things right

So let's get out of the illusion of comparing code one character at a time and try to find an abstraction that can be applied to updating all of these data types. There are two key points of this abstraction that have already been mentioned in the previous section:

  • A change contains the information that can transform the value of an item from one to another
  • Multiple changes could be generated or applied to one data item during a single synchronization

Now, starting from changes, let's think about what happens when an update method of a client is called.

Finding abstraction

Take a closer look to the method update of client:

  • For data of the 'value' type, first we create the change, including a new value, and then update the change list to make the newly created change the only one. After that, we update the value of data item.
  • For data of the 'increment' type, we add a change including the increment in the change list; or if a change that has...

Summary

In this chapter, we've been part of the evolution of a simplified yet reality-related project. Starting with a simple code base that couldn't be wrong, we added a lot of features and experienced the process of putting acceptable changes together and making the whole thing a mess.

We were always trying to write readable code by either naming things nicely or adding semantically necessary redundancies, but that won't help much as the complexity grows.

During the process, we've learned how offline synchronizing works. And with the help of the most common design patterns, such as the Strategy Pattern, we managed to split the project into small and controllable parts.

In the upcoming chapters, we'll catalog more useful design patterns with code examples in TypeScript, and try to apply those design patterns to specific issues.

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Key benefits

  • This step-by-step guide will would demonstrate all the important design patterns in practice
  • This book is the only documentation on the market focusing on design patterns in TypeScript
  • This book is packed with rich examples that will improve your efficiency and encourage code reuse

Description

In programming, there are several problems that occur frequently. To solve these problems, there are various repeatable solutions that are known as design patterns. Design patterns are a great way to improve the efficiency of your programs and improve your productivity. This book is a collection of the most important patterns you need to improve your applications’ performance and your productivity. The journey starts by explaining the current challenges when designing and developing an application and how you can solve these challenges by applying the correct design pattern and best practices. Each pattern is accompanied with rich examples that demonstrate the power of patterns for a range of tasks, from building an application to code testing. We’ll introduce low-level programming concepts to help you write TypeScript code, as well as work with software architecture, best practices, and design aspects.

Who is this book for?

If you are a TypeScript developer, this book is for you. No knowledge of design patterns is required to read this book.

What you will learn

  • Understand the challenges and implications of developing an enterprise application
  • Install and configure the necessary tools in order to start developing an application
  • Identify the challenges when developing an application
  • Apply GoF patterns in an application with a testing approach
  • Use and utilize design patterns while developing a TypeScript application or during JavaScript application development
  • Reference to SOLID principles and what their benefits do to your projects
  • Apply various principles in a TypeScript application
  • Improve code quality and development speed
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Length: 256 pages
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Language : English
ISBN-13 : 9781785280832
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Table of Contents

9 Chapters
1. Tools and Frameworks Chevron down icon Chevron up icon
2. The Challenge of Increasing Complexity Chevron down icon Chevron up icon
3. Creational Design Patterns Chevron down icon Chevron up icon
4. Structural Design Patterns Chevron down icon Chevron up icon
5. Behavioral Design Patterns Chevron down icon Chevron up icon
6. Behavioral Design Patterns: Continuous Chevron down icon Chevron up icon
7. Patterns and Architectures in JavaScript and TypeScript Chevron down icon Chevron up icon
8. SOLID Principles Chevron down icon Chevron up icon
9. The Road to Enterprise Application Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.7
(3 Ratings)
5 star 66.7%
4 star 0%
3 star 0%
2 star 0%
1 star 33.3%
Amazon Customer Oct 10, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book is not only about how design patterns could be used in TypeScript, but also lots of best practice in TS introduced by the author. The Design Pattern itself is important, but why we need it and how to use it is much more important, which has also been introduced in this book
Amazon Verified review Amazon
S S. Sep 13, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Post for my friend WanderWang[1]: This book introduces the best practices of TypeScript development workflow at the beginning of the book. Next, combined with the TypeScript's own syntax characteristics, introduced a lot of design patterns in the TypeScript implementation, I found a lot of examples are from the actual project will be encountered problems and solutions. This book can guide me how to write high-quality TypeScript code, the author did a good work![1] [...]
Amazon Verified review Amazon
Archimedes Oct 23, 2016
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
"Thanks to the efforts of the TypeScript community, almost every popular JavaScript library got its declaration files on a project called DefinitelyTyped. And there has already been a tool called tsd for declaration file management. But soon, people realized the limitation of a single huge repository for everything, as well as the issues tsd cannot solve nicely.""Compile and run; buy me a cup of coffee it it works. But it probably won't."This is just a fraction of the nonsensical English that takes place in chapter one. Clearly English is the author's second language, and the mere fact that he can write a book in a language other than his primary language is really quite astonishing. HOWEVER, I don't like to read broken English and what is clear from page 1 is that this book has not been edited by someone whose first language is English. I would expect that from a book that is nearly $30. I really would have liked to have read the subsequent chapters illustrating GoF design patterns implemented with TypeScript. I just couldn't make it out of chapter 1.
Amazon Verified review Amazon
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