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)

Hello world with TypeScript

Now that you have all the tools at your disposal, let's write the ceremonial Hello World in TypeScript.

Creating the project

Open your favorite Terminal (again, we will assume Bash here). Create a new folder called hello-world:

$ mkdir hello-world

After the previous command, you can go into the newly created folder:

$ cd hello-world

Now open VS Code in the current folder using the code . command.

Hello (Type/Java)Script!

So, TypeScript is a superset of JavaScript, right? Let's see what that actually means by following these steps:

  1. Create a new file called hello-world.ts:
The .ts file extension stands for TypeScript.

You can do it from within VS Code:

As you can see, VS Code directly recognizes TypeScript files:

  1. Now add the following code to your newly created file:
var hello = "Hello world";

function say(something) {
console.log(something);
}

say(hello);

Now let's do a silly thing: let's ask Node (our JavaScript interpreter) to execute our TypeScript code:

$ node hello-world.ts 

The output will be as follows:

That worked? Well, as you have probably guessed, this first example only contains JavaScript, which is why node doesn't have any issue.