Book Image

Mastering TypeScript 3 - Third Edition

By : Nathan Rozentals
Book Image

Mastering TypeScript 3 - Third Edition

By: Nathan Rozentals

Overview of this book

TypeScript is both a language and a set of tools to generate JavaScript. It was designed by Anders Hejlsberg at Microsoft to help developers write enterprise-scale JavaScript. Starting with an introduction to the TypeScript language, before moving on to basic concepts, each section builds on previous knowledge in an incremental and easy-to-understand way. Advanced and powerful language features are all covered, including asynchronous programming techniques, decorators, and generics. This book explores many modern JavaScript and TypeScript frameworks side by side in order for the reader to learn their respective strengths and weaknesses. It will also thoroughly explore unit and integration testing for each framework. Best-of-breed applications utilize well-known design patterns in order to be scalable, maintainable, and testable. This book explores some of these object-oriented techniques and patterns, and shows real-world implementations. By the end of the book, you will have built a comprehensive, end-to-end web application to show how TypeScript language features, design patterns, and industry best practices can be brought together in a real-world scenario.
Table of Contents (16 chapters)
Free Chapter
TypeScript Tools and Framework Options

Writing your own declaration file

In any development team, there will come a time when you will need to either bug-fix, or enhance a body of code that has already been written in JavaScript. If you are in this situation, then you would want to try and write new areas of code in TypeScript, and integrate them with your existing body of JavaScript. To do so, however, you will need to write your own declaration files for any existing JavaScript that you need to reuse. This may seem like a daunting and time-consuming task, but when you are faced with this situation, just remember to take small steps, and define small sections of code at a time. You will be surprised at how simple it really is.

In this section, let's assume that you need to integrate an existing helper class—one that is reused across many projects, is well tested, and is a development team standard. This...