Book Image

The TypeScript Workshop

By : Ben Grynhaus, Jordan Hudgens, Rayon Hunte, Matt Morgan, Vekoslav Stefanovski
5 (1)
Book Image

The TypeScript Workshop

5 (1)
By: Ben Grynhaus, Jordan Hudgens, Rayon Hunte, Matt Morgan, Vekoslav Stefanovski

Overview of this book

By learning TypeScript, you can start writing cleaner, more readable code that’s easier to understand and less likely to contain bugs. What’s not to like? It’s certainly an appealing prospect, but learning a new language can be challenging, and it’s not always easy to know where to begin. This book is the perfect place to start. It provides the ideal platform for JavaScript programmers to practice writing eloquent, productive TypeScript code. Unlike many theory-heavy books, The TypeScript Workshop balances clear explanations with opportunities for hands-on practice. You’ll quickly be up and running building functional websites, without having to wade through pages and pages of history and dull, dry fluff. Guided exercises clearly demonstrate how key concepts are used in the real world, and each chapter is rounded off with an activity that challenges you to apply your new knowledge in the context of a realistic scenario. Whether you’re a hobbyist eager to get cracking on your next project, or a professional developer looking to unlock your next promotion, pick up a copy and make a start! Whatever your motivation, by the end of this book, you’ll have the confidence and understanding to make it happen with TypeScript.
Table of Contents (16 chapters)
Preface

TypeScript and Functions

Another huge benefit of TypeScript is automatic function invocation checking. Let's say that we have the function we used for our first TypeScript file:

function add (x, y) {
    return x + y;
}

Even without any type annotations, TypeScript still has some information about this function – namely, that it takes two, and exactly two, parameters.

In contrast, JavaScript does not enforce that the number of actual arguments has to conform to the number of parameters defined, so all of the following invocations are valid calls in JavaScript:

add(1, 2); // two arguments
add(1, 2, 3); // three arguments
add(1); // one argument
add(); // no arguments

In JavaScript, we can call a function with more arguments than parameters, fewer arguments, or even without any arguments at all. If we have more arguments than needed, the extra arguments are simply ignored (and stored in the magical arguments variable), and if we have...