Book Image

Learning TypeScript 2.x - Second Edition

By : Remo H. Jansen
Book Image

Learning TypeScript 2.x - Second Edition

By: Remo H. Jansen

Overview of this book

TypeScript is an open source and cross-platform statically typed superset of JavaScript that compiles to plain JavaScript and runs in any browser or host. This book is a step-by-step guide that will take you through the use and benefits of TypeScript with the help of practical examples. You will start off by understanding the basics as well as the new features of TypeScript 2.x. Then, you will learn how to work with functions and asynchronous programming APIs. You will continue by learning how to resolve runtime issues and how to implement TypeScript applications using the Object-oriented programming (OOP) and functional programming (FP) paradigms. Later, you will automate your development workflow with the help of tools such as Webpack. Towards the end of this book, you will delve into some real-world scenarios by implementing some full-stack TypeScript applications with Node.js, React and Angular as well as how to optimize and test them. Finally, you will be introduced to the internal APIs of the TypeScript compiler, and you will learn how to create custom code analysis tools.
Table of Contents (17 chapters)

Asynchronous programming in TypeScript

Now that we have seen how to work with functions, we will explore how we can use them, together with some native APIs, to write asynchronous applications.

Callbacks and higher-order functions

In TypeScript, functions can be passed as arguments to another function. Functions can also be returned by another function. A function passed to another as an argument is known as a callback. Functions that accept functions as parameters (callbacks) or return functions are known as higher-order functions.

Callbacks are usually anonymous functions. They can be declared before they are passed to the higher-order function, as demonstrated by the following example:

var foo = function() { // callback...