Book Image

Learn TypeScript 3 by Building Web Applications

By : Sebastien Dubois, Alexis Georges
Book Image

Learn TypeScript 3 by Building Web Applications

By: Sebastien Dubois, Alexis Georges

Overview of this book

TypeScript is a superset of the JavaScript programming language, giving developers a tool to help them write faster, cleaner JavaScript. With the help of its powerful static type system and other powerful tools and techniques it allows developers to write modern JavaScript applications. This book is a practical guide to learn the TypeScript programming language. It covers from the very basics to the more advanced concepts, while explaining many design patterns, techniques, frameworks, libraries and tools along the way. You will also learn a ton about modern web frameworks like Angular, Vue.js and React, and you will build cool web applications using those. This book also covers modern front-end development tooling such as Node.js, npm, yarn, Webpack, Parcel, Jest, and many others. Throughout the book, you will also discover and make use of the most recent additions of the language introduced by TypeScript 3 such as new types enforcing explicit checks, flexible and scalable ways of project structuring, and many more breaking changes. By the end of this book, you will be ready to use TypeScript in your own projects and will also have a concrete view of the current frontend software development landscape.
Table of Contents (15 chapters)

String literal types

A nice alternative to enums and string enums in TypeScript is string literal types. They provide a way to specify the value that a string must have and can actually provide the same kind of behavior as enums. One benefit of string literal types is that you can also combine them with type guards, type aliases, and unions.

The following is an example:

type Mood = "Great" | "Good" | "Bad" | "Awful"; 
const myCurrentMood: Mood = "Great"; // may only be assigned values that are part of the Mood union! 

With the Mood type defined, we can get auto-completion, as shown in the following screenshot:

While using this type, you are, of course, not allowed to pass a value that is not part of the type, hence the similarity with enums.

String literal types are also inlined. If you look at the generated code for the previous...