Book Image

TypeScript 2.x By Example

By : Sachin Ohri
Book Image

TypeScript 2.x By Example

By: Sachin Ohri

Overview of this book

The TypeScript language, compiler, and open source development toolset brings JavaScript development up to the enterprise level. It allows you to use ES5, ES6, and ES7 JavaScript language features today, including classes, interfaces, generics, modules, and more. Its simple typing syntax enables building large, robust applications using object-oriented techniques and industry-standard design principles. This book aims at teaching you how to get up and running with TypeScript development in the most practical way possible. Taking you through two exciting projects built from scratch, you will learn the basics of TypeScript, before progressing to functions, generics, promises, and callbacks. Then, you’ll get to implement object-oriented programming as well as optimize your applications with effective memory management. You’ll also learn to test and secure your applications, before deploying them. Starting with a basic SPA built using Angular, you will progress on to building, maybe, a Chat application or a cool application. You’ll also learn how to use NativeScript to build a cool mobile application. Each of these applications with be explained in detail, allowing you to grasp the concepts fast. By the end of this book, you will have not only built two amazing projects but you will also have the skills necessary to take your development to the next level.
Table of Contents (11 chapters)

Iterators

Iterators are found all over the place in TypeScript and JavaScript. Iterators are the reason we can access values in a sequential manner. Iterators allow us to use functions such as for...of and for...in to access the data in an array.

Some common iterators in TypeScript are arrays, maps, sets, and strings, which allow us to access elements in a linear fashion. For any object to be iteratable, they need to have a Symbol.iterator property. The Symbol.iterator property is a function with methods that allow us to iterate over the elements of an object.

Iterators in JavaScript

First, let's look at a simple example of how we can access the elements of an object in an iterative fashion:

let stringArray = "Learning...