Book Image

TypeScript Design Patterns

By : Vilic Vane
Book Image

TypeScript Design Patterns

By: Vilic Vane

Overview of this book

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.
Table of Contents (15 chapters)
TypeScript Design Patterns
About the Author
About the Reviewer

Memento Pattern

We've talked about an undo support implementation in the previous section on the Command Pattern, and found it was not easy to implement the mechanism purely based on reversing all the operations. However, if we take snapshots of objects as their history, we may manage to avoid accumulating mistakes and make the system more stable. But then we have a problem: we need to store the states of objects while the states are encapsulated with objects themselves.

Memento Pattern helps in this situation. While a memento carries the state of an object at a certain time point, it also controls the process of setting the state back to an object. This makes the internal state implementation hidden from the undo mechanism in the following example:

We have the instances of the memento controlling the state restoration in the preceding structure. It can also be controlled by the caretaker, namely the undo mechanism, for simple state restoring cases.


The participants of Memento...