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TypeScript Blueprints
TypeScript Blueprints

TypeScript Blueprints: Practical Projects to Put TypeScript into Practice

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TypeScript Blueprints

Chapter 2. A Weather Forecast Widget with Angular 2

In this chapter, we'll create a simple application that shows us the weather forecast. The framework we use, Angular 2, is a new framework written by Google in TypeScript. The application will show the weather of the current day and the next. In the following screenshot, you can see the result. We will explore some key concepts of Angular, such as data binding and directives.

A Weather Forecast Widget with Angular 2

We will build the application in the following steps:

  • Using modules
  • Setting up the project
  • Creating the first component
  • Adding conditions to the template
  • Showing a forecast
  • Creating the forecast components
  • The main component

Using modules

We will use modules in all applications in this book. Modules (also called external modules and ES2015 modules) are a concept of separating code in multiple files. Every file is a module. Within these modules, you can use variables, functions, and classes (members) exported by other modules and you can make some members visible for other modules. To use other modules, you must import them, and to make members visible, you need to export them. The following example will show some basic usage:

// x.ts 
import { one, add, Lorem } from './y'; 
console.log(add(one, 2)); 
 
var lorem = new Lorem(); 
console.log(lorem.name); 
 
// y.ts 
export var one = 1; 
export function add(a: number, b: number) { 
  return a + b; 
} 
export class Lorem { 
  name = "ipsum"; 
} 

You can export declarations by prefixing them with the export keyword or by prefixing them with export default. A default export should be imported differently though we will not use such an export as...

Setting up the project

We will quickly set up the project before we can start writing. We will use npm to manage our dependencies and gulp to build our project. These tools are built on NodeJS, so it should be installed from nodejs.org.

First of all, we must create a new directory in which we will place all files. We must create a package.json file used by npm:

{ 
  "name": "weather-widget", 
  "version": "1.0.0", 
  "private": true, 
  "description": "" 
} 

The package.json file contains information about the project, such as the name, version, and a description. These fields are used by npm when you publish a project on the registry on NPM, which contains a lot of open source projects. We will not publish it there. We set the private field to true, so we cannot accidentally publish it.

Directory structure

We will separate the TypeScript sources from the other files. The TypeScript files will be added in the lib directory...

Creating the first component

Angular is based on components. Components are built with other components and normal HTML tags. Our application will have three components: the forecast page, the about page, and the whole widget. The widget itself, which is referenced in the HTML page, will use the other two widgets.

The widget will show the About page in the third tab, as you can see in the following screenshot:

Creating the first component

The forecast component is shown in the first tab of the following screenshot. We will create the forecast and the widget later in this chapter.

Creating the first component

The template

A component is a class decorated with some metadata. Decorators are functions that can modify a class or decorate it with some metadata. A simple component that does not have any interaction will look like this:

import { Component } from "angular2/core"; 
 
@Component({ 
  selector: "about-page", 
template: ` 
    <h2>About</h2> 
    This widget shows the weather forecast of Utrecht. 
    The next...

Adding conditions to the template

The event handler in the previous section sets the property collapsed to false but that does not modify the template. In normal code, we would have written if (this.collapsed) { ... }. In templates, we cannot use that, but we can use ngIf.

Directives

A directive is an extension to normal HTML tags and attributes. It can define custom behavior. A custom component, such as the About page, can be seen as a directive too. The ngIf condition is a built-in directive in Angular. It is a custom attribute that displays the content if the specified value is true.

The template tag

If a piece of a component needs to be shown a variable an amount of times, you can wrap it in a template tag. Using the ngIf (or ngFor) directive, you can control how often it is shown (in case of ngIf, once or zero times). The template tag will look like this:

<template [ngIf]="collapsed"> 
  <div>Content</div> 
</template> 

You can abbreviate this as follows...

Using modules


We will use modules in all applications in this book. Modules (also called external modules and ES2015 modules) are a concept of separating code in multiple files. Every file is a module. Within these modules, you can use variables, functions, and classes (members) exported by other modules and you can make some members visible for other modules. To use other modules, you must import them, and to make members visible, you need to export them. The following example will show some basic usage:

// x.ts 
import { one, add, Lorem } from './y'; 
console.log(add(one, 2)); 
 
var lorem = new Lorem(); 
console.log(lorem.name); 
 
// y.ts 
export var one = 1; 
export function add(a: number, b: number) { 
  return a + b; 
} 
export class Lorem { 
  name = "ipsum"; 
} 

You can export declarations by prefixing them with the export keyword or by prefixing them with export default. A default export should be imported...

Setting up the project


We will quickly set up the project before we can start writing. We will use npm to manage our dependencies and gulp to build our project. These tools are built on NodeJS, so it should be installed from nodejs.org.

First of all, we must create a new directory in which we will place all files. We must create a package.json file used by npm:

{ 
  "name": "weather-widget", 
  "version": "1.0.0", 
  "private": true, 
  "description": "" 
} 

The package.json file contains information about the project, such as the name, version, and a description. These fields are used by npm when you publish a project on the registry on NPM, which contains a lot of open source projects. We will not publish it there. We set the private field to true, so we cannot accidentally publish it.

Directory structure

We will separate the TypeScript sources from the other files. The TypeScript files will be added in the lib directory. Static files, such as HTML and CSS, will...

Creating the first component


Angular is based on components. Components are built with other components and normal HTML tags. Our application will have three components: the forecast page, the about page, and the whole widget. The widget itself, which is referenced in the HTML page, will use the other two widgets.

The widget will show the About page in the third tab, as you can see in the following screenshot:

The forecast component is shown in the first tab of the following screenshot. We will create the forecast and the widget later in this chapter.

The template

A component is a class decorated with some metadata. Decorators are functions that can modify a class or decorate it with some metadata. A simple component that does not have any interaction will look like this:

import { Component } from "angular2/core"; 
 
@Component({ 
  selector: "about-page", 
template: ` 
    <h2>About</h2> 
    This widget shows the weather forecast of Utrecht. 
...

Adding conditions to the template


The event handler in the previous section sets the property collapsed to false but that does not modify the template. In normal code, we would have written if (this.collapsed) { ... }. In templates, we cannot use that, but we can use ngIf.

Directives

A directive is an extension to normal HTML tags and attributes. It can define custom behavior. A custom component, such as the About page, can be seen as a directive too. The ngIf condition is a built-in directive in Angular. It is a custom attribute that displays the content if the specified value is true.

The template tag

If a piece of a component needs to be shown a variable an amount of times, you can wrap it in a template tag. Using the ngIf (or ngFor) directive, you can control how often it is shown (in case of ngIf, once or zero times). The template tag will look like this:

<template [ngIf]="collapsed"> 
  <div>Content</div> 
</template> 

You can abbreviate this as follows...

Using the component in other components


We can use the about-page component in other components, as if it was a normal HTML tag. But the component is still boring, as it will always say that it shows the weather broadcast of Utrecht. We can mark the location property as an input. After that, location is an attribute that we can set from other components. It is even possible to bind it as a one-way binding. The Input decorator, which we are using here, needs to be imported just like Component:

import { Component, Input } from "angular2/core"; 
 
@Component({ 
  ... 
}) 
export class About { 
  @Input()

  location: string = "Utrecht"; 
  collapsed = true; 
  show() { 
    this.collapsed = false; 
  } 
  hide() { 
    this.collapsed = true; 
  } 
 
  get encodedLocation() { 
    return encodeURIComponent(this.location); 
  } 
} 
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Key benefits

  • Follow and build every featured projects to put the principles of TypeScript into practice
  • Learn how to use TypeScript alongside other leading tools such as Angular 2, React, and Node.js
  • Find out how to migrate your JavaScript codebase to TypeScript

Description

TypeScript is the future of JavaScript. Having been designed for the development of large applications, it is now being widely incorporated in cutting-edge projects such as Angular 2. Adopting TypeScript results in more robust software - software that is more scalable and performant. It's scale and performance that lies at the heart of every project that features in this book. The lessons learned throughout this book will arm you with everything you need to build some truly amazing projects. You'll build a complete single page app with Angular 2, create a neat mobile app using NativeScript, and even build a Pac Man game with TypeScript. As if fun wasn't enough, you'll also find out how to migrate your legacy codebase from JavaScript to TypeScript. This book isn't just for developers who want to learn - it's for developers who want to develop. So dive in and get started on these TypeScript projects.

Who is this book for?

This is for web developers committed to building better software. It's for web developers that know writing code should be fun - and that fun and creativity are the foundations of better software products.

What you will learn

  • Build quirky and fun projects from scratch
  • Use TypeScript with a range of different technologies such as Angular 2 and React
  • Migrate JavaScript codebases to TypeScript to improve your workflow
  • Write maintainable and reusable code
  • Using System.JS and Webpack to load scripts and their dependencies.
  • Developing highly performance server-side applications to run within Node.js
  • Reviewing high performant Node.js patterns and manage garbage collection

Product Details

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Publication date : Jul 28, 2016
Length: 288 pages
Edition : 1st
Language : English
ISBN-13 : 9781785887017
Vendor :
Microsoft
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Length: 288 pages
Edition : 1st
Language : English
ISBN-13 : 9781785887017
Vendor :
Microsoft
Languages :
Tools :

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Table of Contents

10 Chapters
1. TypeScript 2.0 Fundamentals Chevron down icon Chevron up icon
2. A Weather Forecast Widget with Angular 2 Chevron down icon Chevron up icon
3. Note-Taking App with a Server Chevron down icon Chevron up icon
4. Real-Time Chat Chevron down icon Chevron up icon
5. Native QR Scanner App Chevron down icon Chevron up icon
6. Advanced Programming in TypeScript Chevron down icon Chevron up icon
7. Spreadsheet Applications with Functional Programming Chevron down icon Chevron up icon
8. Pac Man in HTML5 Chevron down icon Chevron up icon
9. Playing Tic-Tac-Toe against an AI Chevron down icon Chevron up icon
10. Migrate JavaScript to TypeScript Chevron down icon Chevron up icon
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