TypeScript Blueprints

By Ivo Gabe de Wolff

About This Book

• This book will help you whether you’re a beginner or an expert
• Complete and complex projects provide codes that are ready and solutions for start-ups and enterprise developers
• The book will showcase the power and depth of TypeScript when it comes to high performance and scalability

Who This Book Is For

This book was written for web developers who wish to make the most of TypeScript and build fun projects. You should be familiar with the fundamentals of JavaScript, and basic knowledge of TypeScript is useful.

• Language: English
• Publisher: Packt Publishing
• Release date: Jul 28, 2016
• ISBN: 9781785888779

Book preview

Table of Contents

TypeScript Blueprints

Credits

About the Author

About the Reviewer

www.PacktPub.com

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book 

Errata

Piracy

Questions

1. TypeScript 2.0 Fundamentals

What is TypeScript?

Quick example

Transpiling

Type checking

Learning modern JavaScript

let and const

Classes

Arrow functions

Function arguments

Array spread

Destructuring

Template strings

New classes

Type checking

Primitive types

Defining types

Undefined and null

Type annotations

Summary

2. A Weather Forecast Widget with Angular 2

Using modules

Setting up the project

Directory structure

Configuring TypeScript

Building the system

The HTML file

Creating the first component

The template

Testing

Interactions

One-way variable binding

Event listeners

Adding conditions to the template

Directives

The template tag

Modifying the about template

Using the component in other components

Showing a forecast

Using the API

Typing the API

Creating the forecast component

Templates

Downloading the forecast

Adding @Output

The main component

Using our other components

Two-way bindings

Listening to our event

Geolocation API

Component sources

Summary

3. Note-Taking App with a Server

Setting up the project structure

Directories

Configuring the build tool

Type definitions

Getting started with NodeJS

Asynchronous code

Callback approach for asynchronous code

Disadvantages of callbacks

The database

Wrapping functions in promises

Connecting to the database

Querying the database

Understanding the structural type system

Generics

Typing the API

Adding authentication

Implementing users in the database

Adding users to the database

Testing the API

Adding CRUD operations

Implementing the handlers

Request handling

Writing the client side

Creating the login form

Creating a menu

The note editor

The main component

Error handler

Running the application

Summary

4. Real-Time Chat

Setting up the project

Configuring gulp

Getting started with React

Creating a component with JSX

Adding props and state to a component

Creating the menu

Testing the application

Writing the server

Connections

Typing the API

Accepting connections

Storing recent messages

Handling a session

Implementing a chat message session

Connecting to the server

Automatic reconnecting

Sending a message to the server

Writing the event handler

Creating the chat room

Two-way bindings

Stateless functional components

Running the application

Comparing React and Angular

Templates and JSX

Libraries or frameworks

Summary

5. Native QR Scanner App

Getting started with NativeScript

Creating the project structure

Adding TypeScript

Creating a Hello World page

Creating the main view

Adding a details view

Scanning QR codes

Type definitions

Implementation

Testing on a device

Adding persistent storage

Styling the app

Comparing NativeScript to alternatives

Summary

6. Advanced Programming in TypeScript

Using type guards

Narrowing

Narrowing any

Combining type guards

More accurate type guards

Assignments

Checking null and undefined

Guard against null and undefined

The never type

Creating tagged union types

Comparing performance of algorithms

Big-Oh notation

Optimizing algorithms

Binary search

Built-in functions

Summary

7. Spreadsheet Applications with Functional Programming

Setting up the project

Functional programming

Calculating a factorial

Using data types for expressions

Creating data types

Traversing data types

Validating an expression

Calculating expressions

Writing unit tests

Parsing an expression

Creating core parsers

Running parsers in a sequence

Parsing a number

Order of operations

Defining the sheet

Calculating all fields

Using the Flux architecture

Defining the state

Creating the store and dispatcher

Creating actions

Adding a column or a row

Changing the title

Showing the input popup

Testing actions

Writing the view

Rendering the grid

Rendering a field

Showing the popup

Adding styles

Gluing everything together

Advantages of Flux

Going cross-platform

Summary

8. Pac Man in HTML5

Setting up the project

Using the HTML5 canvas

Saving and restoring the state

Designing the framework

Creating pictures

Wrapping other pictures

Creating events

Binding everything together

Drawing on the canvas

Adding utility functions

Creating the models

Using enums

Storing the level

Creating the default level

Creating the state

Drawing the view

Handling events

Working with key codes

Creating the time handler

Running the game

Adding a menu

Changing the model

Rendering the menu

Handling events

Modifying the time handler

Summary

9. Playing Tic-Tac-Toe against an AI

Creating the project structure

Configure TypeScript

Adding utility functions

Creating the models

Showing the grid

Creating operations on the grid

Creating the grid

Adding tests

Random testing

Implementing the AI using Minimax

Implementing Minimax in TypeScript

Optimizing the algorithm

Creating the interface

Handling interaction

Creating players

Testing the AI

Testing with a random player

Summary

10. Migrate JavaScript to TypeScript

Gradually migrating to TypeScript

Adding TypeScript

Configuring TypeScript

Configuring the build tool

Acquiring type definitions

Testing the project

Migrating each file

Converting to ES modules

Correcting types

Adding type guards and casts

Using modern syntax

Adding types

Refactoring the project

Enable strict checks

Summary

TypeScript Blueprints

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TypeScript Blueprints

Copyright © 2016 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: July 2016

Production reference: 1250716

Published by Packt Publishing Ltd.

Livery Place

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B3 2PB, UK.

ISBN 978-1-78588-701-7

www.packtpub.com

Credits

About the Author

Ivo Gabe de Wolff has been a freelance developer under the name of ivogabe since 2012 and he is studying mathematics and computing sciences at Utrecht University. When he was eleven he started programming in Game Maker. Currently, he uses TypeScript on a daily basis. Recently, he has used TypeScript in lots of different environments, including mobile apps, servers, and command-line tools. Now he mainly specializes in NodeJS programming.

Furthermore, he is the author of various open source projects, including gulp-typescript. You can find his projects on github.com/ivogabe . If you want to read more about TypeScript, JavaScript, gulp, or Functional Programming, you can take a look at his blog at dev.ivogabe.com .

It required a lot of work to compose this book. I could not have done this without the help of these people:

The team at Packt Publishing and the reviewers of this book, because of their precise feedback and hard work. This has helped me a lot to improve the quality of this book.

My fellow students, for brainstorming and helping on specific topics.

My teachers at Utrecht University, for giving inspiration and challenging me on various topics. I especially want to thank Jurriaan Hage for supervising my thesis.

Finally, my family, for their support and tips, even though they did not have knowledge on these topics. These people have helped me to to make the book as it now lies in front of you.

About the Reviewer

Matthew Hill is a British software developer with substantial experience in web application development. An established developer in the TypeScript and JavaScript spheres, he thoroughly enjoys working on open source projects and dipping into often esoteric technologies. Outside of programming, Matthew has a fervent interest in literature.

After graduating with a computer science degree, he started his career at Sky UK Ltd, where he developed video streaming applications, subsequently moving on to engineer single-page analytics applications at payments startup Velocity. Now he’s working at financial services leader Tradeweb, fleshing out their next-generation JavaScript-based trading platform.

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Preface

TypeScript allows developers to write readable and maintainable web applications. Editors can provide several tools to the developer, based on types and static analysis of the code. In this book, you will learn how you can use TypeScript to build clean web applications. You will learn how to use Angular 2 and React.

You will also learn how you can use TypeScript for servers, mobile apps, command-line tools, and games. We will build various servers, write a mobile app, rewrite Pac Man, and build Tic-Tac-Toe as a command-line application. You will also learn functional programming. This style of programming will improve your general code skills. You will see how this style can be used in TypeScript.

What this book covers

The book can be divided in two sections. The first section, chapters 1 to 4, describe how you can build standard application. These chapters introduce Angular 2 and React for web applications, NodeJS for servers and NativeScript for mobile apps. You should read chapters 1 to 3 in a sequence.

The second section, chapters 5 to 8, introduce more complex concepts. You will learn functional programming in chapters 5 to 7. The last chapter contains guidance to migrate a JavaScript codebase to TypeScript. You can read chapters 5 to 7 when you have not read chapters 1 to 4, though chapter 5 requires some knowledge of React.

Chapter 1, TypeScript 2.0 Fundamentals, will explain core principals to create (web) applications with TypeScript. If you have some basic knowledge of TypeScript 2.0 then you can skim over this chapter or use it as a reference while reading the other chapters. If you have not used TypeScript yet, then this chapter will teach you the fundamentals of TypeScript 2.0

Chapter 2, A Weather Forecast Widget with Angular 2, you will learn how you can build an application in Angular 2. The chapter introduces core principals of Angular and will use an online API as source for the weather forecast.

Chapter 3, Note-Taking App with a Server, we will build a server and client with Node and Angular for this application. You will see how code can be shared between the client and the server.

Chapter 4, Real-Time Chat, introduces React and websockets. Using these techniques, we will write the server and client of the chat application.

Chapter 5, Native QR Scanner App, after having written three web applications, we will now write a mobile app. You will learn how you can use NativeScript and its plugins to write a native app.

Chapter 6, Advanced Programming in TypeScript,  covers more advanced features of TypeScript, including type guards, control flow analysis and performance of algorithms.

Chapter 7, Spreadsheet Applications with Functional Programming, introduces a different programming style: functional programming. You will learn how this can be used in TypeScript. We will use React with a Flux-based architecture, which fits nicely with TypeScript and Functional Programming.

Chapter 8, Pac Man in HTML5, will show how to use the HTML5 canvas to create a game. We will use some Functional Programming again, and take a look at how we can create a framework for it based on the Flux architecture.

Chapter 9, Playing Tic-Tac-Toe against an AI, will explain how to build a command-line application in which you can play Tic-Tac-Toe. You will learn how you can learn the computer to play the game. When done correctly, the computer should never lose.

Chapter 10, Migrate JavaScript to TypeScript, will show how you can incrementally migrate a JavaScript codebase to TypeScript. We will focus on how you can keep the project working during this transition.

What you need for this book

You will need an editor to write the code, a terminal to compile the code, and a browser to see the results. Visual Studio Code and Atom with atom-typescript are good editors in which you can write TypeScript code. These are available for Windows, Mac, and Linux. You have to compile TypeScript in a terminal. On Windows, you can use the Command Prompt or Powershell for that. On a Mac, you can use Terminal.

To compile TypeScript, you need NodeJS. You can find details on how you can install it in the first chapter.

Chapter 5, Native QR Scanner App, has more requirements to run the mobile app in an emulator or a device. Details about how you can install these dependencies are found in the chapter.

Who this book is for

If you are interested in building fun projects using TypeScript, then this book is for you. This book will appeal to web developers who wish to make the most of TypeScript. You should be familiar with the fundamentals of JavaScript.

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: We can include other contexts through the use of the include directive.

A block of code is set as follows:

export function factorial(x: number): number {

   if (x <= 1) return 1;

   return x * factorial(x - 1);

}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

export function factorial(x: number): number {

   if (x <= 1) return 1;

 

  return x * factorial(x - 1);

 

}

Any command-line input or output is written as follows:

npm init -y

New terms and important words are shown in bold. 

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

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Errata

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