README.md

Angular 2/4/5/6/7

Welcome

Hi All, I'm Dinanath Jayaswal, Senior UI/Web Developer and Adobe Certified Expert Professional, I wanna welcome you to Angular7 step by step guide. In this course/tutorial will go over and learn all the fundamental building blocks of Angular, which a developer needs to know to get started developing Angular applications. Will cover from Node/NPM/Angular CLI Setup, Angular basic+advanced and common concepts like Components, Interpolation, Data Binding, Pipes, Services, Directives, Routing and Nativation, Forms, Http and Observables, etc.

Who is this for?

This course is for anyone and everyone, Almost everyone! Fresher/Newcomer as well as experienced UI/frontend/Web Developers who are interested in boost skills and further career - by learning new latest dynamic JavaScript framework from Google to become a hi-tech developer.

Topics include

1. Angular7 Introduction
2. Getting Started
3. Angular First Hello World App
4. Components
5. Interpolation (Data Binding)
6. Property Binding
7. Class Binding
8. Style Binding
9. Event Binding
10. Template Reference Variables
11. Two Way Data Binding
12. ngIf Directive
13. ngSwitch Directive
14. ngFor Directive
15. Component Interaction
16. Pipes
17. Services
18. Dependency Injection (DI)
19. Using a Service
20. HTTP and Observables
21. Fetch Data Using HTTP and Observables
22. Creating Custom Directives
23. Custom Directives with Events and @HostListener
24. Creating Custom Pipes

01 Angular7 Introduction

1.1. What is Angular:

• Angular is a JavaScript (TypeScript based) open-source front-end web application framework from Google
• A framework to build a client-side application
• Great for SPAs (Single Page Application)
• Angular Ver2/4/5/6/7 frameworks target Mobile and Desktop
• The very first version Angular 1.0 (1.xx) is known as AngularJS, versions beyond 2+ are generally known as Angular

1.2. SPA (Single Page Application)

A SPA (Single Page Application) is a website/web applications in which part of page reload asynchronously without loading/re-loading whole page/app. It contains the menu, navigations, buttons, and blocks on a single page, as-and-when a user clicks on any of them; it dynamically rewrites/loads the current page rather than loading entire new pages from a server and so it is reactive, fast and speedy. (Web apps that load a single HTML page and dynamically update that page as the user interacts with the app).

1.3. Why to learn and use Angular:

• Modular approach
• Re-usable code (Components)
• Development quicker and easier (Many inbuilt features helps to do development quicker+easier)
• Follows good programming practices and design patterns (MVC - Module View Controller)
• Inbuilt validations & Routing capabilities)
• Unit testable code
• Easily maintainable code
• Uses advanced features and principles like Dependency Injection, DRY (Do Not Repeat Yourself)
• Google + Microsoft collaboration (Angular + TypeScript)

1.4. Angular History:

• The first version of Angular was Angular1.0 (AngularJS) which was released in 2010

Year	Version
AngularJs = year 2010 = v1.XX (1.0 version)
Angular = year 2016 = Angular v2.0 and above (2/4/5/6/7 and coming future versions...)
2010	Angular JS (Angular v1.XX versions)
2016	Angular v2.0
Version v3.0 skipped to avoid routing version 3.3.0
2016 December	Angular v4.0
2017 November	Angular v5.0
2018 April	Angular v6.0
2018 October	Angular v7.0

1.5. Difference between AngularJS and Angular
What’s new in Angular compared to AngularJS

Let’s focus through some of the main differences between AngularJS and Angular:

AngularJs	Angular
	Angular is a complete rewrite of AngularJS
AngularJS is the name of the first version of v1.XX (1.0 version).	Angular is the name of the Angular's version beyond 2+ (Angular v2.0 and above i.e. 2/4/5/6/7 and coming future angular versions...)
AngularJS is a JavaScript based open-source front-end web application framework.	Angular is a JavaScript/TypeScript/Dart based open-source front-end web application framework.
AngularJS uses the concept of scope($scope) or controller.	Angular uses a hierarchy of components as its primary architectural base.
AngularJS has a simple syntax and uses to work with different directives like ng-app, ng-init, ng-model, ng-for etc.	In Angular syntax have been changed as it uses [ ] for property binding, and ( ) for event binding.

1.6. Semantic Versioning System:

• Change is nature's thumb rule, so every tool/technology/framework/library developed have to room for improvement
• Google team decided and declared that Angular major version will be upgraded twice a year with Semantic Versioning System
• Semantic Versioning System = Major.Minor.Fix Patch, example: 0.0.1
  • Fix Patch - can increase any time with bug fixes/patch release
  • Minor version - increases with every feature release which does not break any functionalities
  • Major version - Break in the functionalities/ extraordinary feature achievements

02 Getting Started

2.1. Pre-requisites:

Basic familiarity with HTML, CSS and JavaScript is must.

• HTML - Markup
• CSS - Style, Formates
• JavaScript - Behaviour, Click, Validations
• TypeScript basics - Advanced JS features (Class, Arrow Function, Spread Operator)
• Text Editor / Visual Text Editors

2.2. Setup the Angular development environment:

In this section, we will learn how to set up a local development environment to start developing Angular apps.

• Node, (website: https://nodejs.org/en)
• NPM, (Node Package Manager - comes inbuilt with Node)
• Angular CLI = Command Line Interface, Angular CLI (Command Line Interface) for angular (website: https://cli.angular.io/),
  • it allows the developer to build/generate building blocks of angular application like component, services, routings, modules, etc. with best practices quicker and easier)
• Text Editor
  • Visual Studio Code / Visual Studio Code Insiders (website: https://code.visualstudio.com)
  • Sublime Text,
  • Atom,
  • Brackets etc.

2.3. Steps to Setup the Angular development environment:

1. Download and Install node (node comes with npm) (website: https://nodejs.org/en)

   

    Image - Nodejs website - https://nodejs.org/en

2. After installation check version of node and npm by command: node -v / node --version OR npm -v / npm --version
3. Install Angular CLI (website https://cli.angular.io/) by using command: npm install -g @angular/cli (it will install Angular CLI globally)

   

    Image - Angular CLI website - https://cli.angular.io/

4. After installation check version of angular CLI by using the command: ng -v OR ng --version, you can also verify angular CLI installation by command: ng OR ng --help
5. Create a new app with angular CLI by using syntax: ng new project/appName example: command: ng new angular6-1-demo
6. Go inside the project/app directory, command: cd angular6-1-demo
7. Build and run Angular App, command: ng serve OR ng serve -o OR ng serve --open
8. Go to the browser and launch/check Angular App by entering the web address: localhost:4200

2.4. Commonly / widely used node/npm commands:

• to get Node version, type command: node -v OR node --version
• to get NPM version, type command: npm -v OR npm --version
• to install Angular CLI, type command: npm install -g @angular/cli
• to get angular CLI version, type command: ng -v OR ng --version (this command displays details of a node, npm, and other angular package versions)
• to get various angular CLI commands, type command: ng OR ng --help

03 Angular First Hello World App

3.1. Creating new Angular App

• If using Visual Studio Code / Insiders, open Command panel/terminal from menu: View -> Terminal (shortcut key is CTRL + BackTick OR COMMAND + J)
• To create a new app with angular CLI by using syntax: ng new project/appName example: command: ng new angular6-1-demo
• Go inside the project/app directory, command: cd angular6-1-demo OR cd appName
• To Build and run Angular App, command: ng serve / npm start OR ng serve -o OR ng serve --open
• To change port from 4200 to other port - type command: ng serve --port 5000
• To check the application in browser type path/url: localhost:4200 / 5000

3.2. Working with existing/cloned/copied Angular App

• Clone or Download the project/app from Github or any other sources
• If using Visual Studio Code / Insiders, open Command panel/terminal from menu: View -> Terminal (shortcut key is CTRL + BackTick OR COMMAND + J)
• Go inside the project/app directory, command: cd _examples-angular6-1-demo OR cd appName
• Run command: npm install to install project/app dependencies (node_modules)
• To Build and run Angular App, command: ng serve / npm start OR ng serve -o OR ng serve --open
• To change port from 4200 to other port - type command: ng serve --port 5000
• To check the application in browser type path/url: localhost:4200 / 5000

3.3. Angular application Architecture summary:

• Angular app: (Show graphical representation of src -> app -> components folder)
  • Angular apps are modular in nature
  • Consists of one or more modules (Angular App is a collection of one or many modules)
  • Modules are main feature area - User module, Admin module, Dashboard module, Employee module)
  • Angular Application Root Module is AppModule (app.module.ts)
  • Modules are lines of code which can be IMPORTed or EXPORTed
    • Module consists of one or more Components and Services
    • Components - .HTML Template + .ts Class + .CSS
      • A component represents/controls view in the browser
      • (example: header, footer, sidebar, common panels, common search utility, similar feature components used throughout the application)
      • Angular Application Root (bootstrapped) component is AppComponent (app.comoponent.ts)
    • Services - Class which consists of Business logic (common programming feature used throughout the application)

   

    Image - Angular Application Folder Architecture

Modules interact and ultimately render Components+Services view in the browser.

3.4. Angular application File / Folder Architecture summary:

• package.json: consists of Node/NPM library/package/module dependencies for application development
• node_modues - folder consists of all installed packages
• src/main.ts - entry point to angular application. src/index.html
• app/app.module.ts - route module of application
• app/app.component.ts - route component of application
• ng serve / npm start -> main.ts (index.html) -> app.module.ts -> app.component.ts -> (app.component.html + css)

04 Components

• The core/key idea behind Angular is to build application using reusable parts/chunks i.e. components
• Components are main building blocks of UI and an/any angular application. (Show graphical representation)
• Angular Application Root (bootstrapped) component is AppComponent (app.comoponent.ts)

   

    Image - Angular Components

A component is self contained, reusable piece of UI made up of 3 important parts:

1. Template - View, HTML code (User Interface for application also known as view)
2. Class - Business logic/Application logic for the view, TypeScript/JavaScript code, (Data, Methods & properties)
3. Decorator/Metadata - Metadata, a @function which provide more information for angular class. example: app.component.ts:

Syntax & Example: app.component.ts

@Component({
    selector: 'app-root', // selector - a custom html tag
    templateUrl: './app.component.html', // template/templateUrl - html view,
    styleUrls: ['./app.component.css'] // styleUrls - css style sheet
})

4.1. Creating component:

• We can create component manually, but in that scenario, we need to do and follow various steps/manual entries
• It's advisable to use angular CLI to create a component, services, routing, etc. To create a component using angular CLI:
  • syntax: ng generate component componentName OR ng generate component path/componentName
  • command: ng generate component components/component-demo1 OR ng g c components/component-demo1
  • It generates 4 new files: .css-styles, .html-markup, .spec.ts-test, .ts-class
  • Also, an automated import /update/entry of components is done in app.module.ts file at the top imports section and in declarations array which consists of all the components used in the application
  • A component must be a member of/belongs to an @NgModule - declarations array in order for it to be usable by another component or application
  • To use current component in application, copy and paste new component 'selector' from .ts file i.e. 'app-component-demo1' as a tag in app.component.html

4.2. @Component/Decorator/Metadata details:

4.2.1. selector:

• Selector is basically a custom HTML tag used to represent current component
• Selector helps to render .html file/html template in browser
• Example: index.html: <app-root></app-root>
• Example: app.component.html: <app-component-demo1><app-component-demo1>
• There are total 3 ways to specify/write and use selectors:

Syntax & Example: component-demo1.component.ts

    1. tag: < > selector: 'app-test', example: <app-test>
    2. class: . selector: '.app-test', example: <div class="app-test">
    3. attribute / [ ]: selector: '[app-test]', example: <div app-test>

4.2.2. template:

• template property denotes writing html markup in current class .ts file only
• template property can help to write all html/markup in .ts typescript file itself
• single line can be written directly:

Syntax & Example:

template: '<h1>Inline single template Heading used - template written in same .ts file</h1>',

• multi line html can be written with back-tick symbol:

Syntax & Example:

template: `
    <h1> Multiple line template </h1>
    <div> template written in same .ts file </div>
`,

4.2.3. templateUrl:

• templateUrl denotes/points to an external .html file OR
• Write html code in another .html file and call the file path with templateUrl property (separation of concern)

Syntax & Example:

templateUrl: './app.component.html', // template/templateUrl - html view,

Syntax & Example: component-demo2-template.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo2-template',
  templateUrl: './component-demo2-template.component.html',

  // single line template
  // template: '<h1>Inline single template para used </h1>',

  // multi line template
  template:`
    <h1>component-demo2-template templateUrl works!</h1>

    <h2>template</h2>
    template denotes writing html markup in current class file only, template property can help to write all html/markup in .ts typescript file itself.
  
    <p> Multiple line template </p>
    <div> template written in same .ts file </div>
    `,
  styleUrls: ['./component-demo2-template.component.css']
})
export class ComponentDemo2TemplateComponent implements OnInit {

  constructor() { }

  ngOnInit() {
  }

}

4.2.4. styles:

• style denotes writing css style for current component only - like inline css,
• multiple css styles written inside array [ ] and back tick symbol

Syntax & Example:

styles: [`
    h1 {
        text-align:center;
    }

    div {
        border:2px dashed gray;
    }
`]

4.2.5. styleUrls:

• styleUrls denotes external css file used for current component
• write css styles in another .css file and call the file path with styleUrls property (seperation of concern)

Syntax & Example:

styleUrls: ['./app.component.css'] // styleUrls - css style sheet

Syntax & Example: component-demo3-styles.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo3-styles',
  templateUrl: './component-demo3-styles.component.html',
  //styleUrls: ['./component-demo3-styles.component.css']
  styles: [`
    h1{
      text-align:center;
    }

    div{
      border:2px dashed gray;
    } 
  `]
})
export class ComponentDemo3StylesComponent implements OnInit {

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo1.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  // 1. <tag/element> selector
  selector: 'app-component-demo1',
  // 2. .class selector
  // selector: '.app-component-demo1',
  // 3. [attribute] selector
  // selector: '[app-component-demo1]',
  templateUrl: './component-demo1.component.html',
  styleUrls: ['./component-demo1.component.css']
})
export class ComponentDemo1Component implements OnInit {
  private appName:string = 'Angualr 6 Application';

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo1.component.html

<div>
  <h1>component-demo1 works! </h1>
  <ul>
    <li>{{ appName }}</li>
  </ul>

  <h2>What is Angular</h2>
  <ul>
    <li>Framework to build client side application</li>
    <li>Great for SPAs</li>
    <li>Angular 2/4/5/6/7 frameworks targets Mobile and Desktop.</li>
  </ul>
</div>

Syntax & Example: app.component.html

<!--The content below is only a placeholder and can be replaced.-->
<div class="container">

  <!-- There are total 3 ways to specify/write and use selectors: 
      tag: < >
      class: .
      attribute / [ ]
    -->

  <app-component-demo1></app-component-demo1>
  <!-- <div class="app-component-demo1"></div> -->
  <!-- <div app-component-demo1></div> -->
  <div class="custom-divider"></div>
</div>

Syntax & Example: app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  // create a property to send from parent to child
  parentMessage = 'From Parent';

  // 
  
}

Syntax & Example: app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { ComponentDemo1Component } from './componenets/component-demo1/component-demo1.component';

@NgModule({
  declarations: [
    AppComponent,
    ComponentDemo1Component,
  ],
  imports: [
    BrowserModule,
  ],

  bootstrap: [AppComponent]
})
export class AppModule { }

Syntax & Example: styles.css

/* You can add global styles to this file, and also import other style files */

/* common global generic styles */
.custom-divider {
  margin: 30px 0px;
  border-bottom:2px dashed gray;
}

h1,h2,h3 {
  text-transform: uppercase;
  /* text-transform: capitalize; */
}

h2 {
  text-decoration: underline;
}

body {
  font-family: Cambria, Cochin, Georgia, Times, 'Times New Roman', serif;
  letter-spacing: 2px;
}

li {
  margin: 10px 0px;
}

input{
  padding: 5px;
}

button {
  border-radius: 5px;
  padding: 10px 15px;
  background-color: teal;
  border: none;
  outline: none;
  cursor: pointer;
  color: lightcyan;
}

/* class binding */
.text-primary {
  color: blue;
}

.text-danger {
  color: red;
}

.text-success {
  color: lawngreen;
}

.text-special {
  font-weight:bold;
  font-style: italic;
  color:orchid;
}

.text-strikethrough {
  text-decoration: line-through;
}

Syntax & Example: index.html

<!doctype html>
  <html lang="en">
    
    <head>
      <meta charset="utf-8">
      <title>Angular7Demo</title>
      <base href="/">

      <meta name="viewport" content="width=device-width, initial-scale=1">
      <link rel="icon" type="image/x-icon" href="favicon.ico">
    </head>

    <body>
      <app-root></app-root>
    </body>

  </html>

   

    Image - Output - selector, templateUrl, styleUrls

05 Interpolation Data Binding

• Interpolation denotes/evaluates the content inside {{ }} braces and displays the value in component view file
• Interpolation = expressions, data-binding to text nodes and attribute values
• interpolation expression = {{ varName }} or {{ fn_anyReturnFunction() }}
• Angular expressions are much like JavaScript expressions and they can contain literals, operators, and variables
• Data binding in Angular is the synchronization/communication between the model and the view
• String interpolation is used to display dynamic data on HTML template (front end / at user end)
• Variable value assignment not possible with interpolation, Example: {{ name = 'Dinanath' or Total = 10 + 20 }}

Syntax & Example: component-demo4-interpolation.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo4-interpolation',
  templateUrl: './component-demo4-interpolation.component.html',
  styleUrls: ['./component-demo4-interpolation.component.css']
})
export class ComponentDemo4InterpolationComponent implements OnInit {
  // variables - class members
  public technology = 'Angular 6';
  public userName = 'Dinanath';
  // public siteUrl = 'http://www.google.com';
  public siteUrl = window.location.href;

  fn_showGreetingsToUser() {
    return 'Welcome ' + this.userName;
  }

  fn_showMessage() {
    return 'Welcome to ' + this.technology + ' ' + this.userName;
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo4-interpolation.component.html

<div>
  <h1>component-demo4-interpolation works!</h1>
  <ul>
    <li>maths = 2+2 = {{ 2+2 }}</li>
    <li>{{ "Welcome " + userName }}</li>
    <li>userName.length = {{ userName.length }}</li>
    <li>toUpperCase = {{ userName.toUpperCase() }}</li>
    <li>toLowerCase = {{ userName.toLowerCase() }}</li>
    <li>current Site URL: {{ siteUrl }}</li>
    <li>function call: {{ fn_showGreetingsToUser() }}</li>
    <li>function call: {{ fn_showMessage() }}</li>
  </ul>
</div>

Syntax & Example: app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { ComponentDemo1Component } from './componenets/component-demo1/component-demo1.component';
import { ComponentDemo2TemplateComponent } from './componenets/component-demo2-template/component-demo2-template.component';
import { ComponentDemo3StylesComponent } from './componenets/component-demo3-styles/component-demo3-styles.component';
import { ComponentDemo4InterpolationComponent } from './componenets/component-demo4-interpolation/component-demo4-interpolation.component';
import { ComponentDemo5PropertybindingComponent } from './componenets/component-demo5-propertybinding/component-demo5-propertybinding.component';

@NgModule({
  declarations: [
    AppComponent,
    ComponentDemo1Component,
    ComponentDemo2TemplateComponent,
    ComponentDemo3StylesComponent,
    ComponentDemo4InterpolationComponent,
  ],
  imports: [
    BrowserModule,
  ],

  bootstrap: [AppComponent]
})
export class AppModule { }

Syntax & Example: app.component.html

<!--The content below is only a placeholder and can be replaced.-->
<div class="container">

  <!-- There are total 3 ways to specify/write and use selectors: 
      tag: < >
      class: .
      attribute / [ ]
    -->

  <app-component-demo1></app-component-demo1>
  <!-- <div class="app-component-demo1"></div> -->
  <!-- <div app-component-demo1></div> -->
  <div class="custom-divider"></div>

  <!-- component decorator template -->
  <app-component-demo2-template></app-component-demo2-template>
  <div class="custom-divider"></div>

  <!-- css style -->
  <app-component-demo3-styles></app-component-demo3-styles>
  <div class="custom-divider"></div>

  <!-- interpolation -->
  <app-component-demo4-interpolation></app-component-demo4-interpolation>
  <div class="custom-divider"></div>

</div>

   

    Image - Output - Interpolation Data Binding {{ }}

06 Property Binding

• String Interpolation and Property binding both are used for the same purpose i.e. one-way Data Binding
• String Interpolation and Property Binding both flow value in one direction from our components to HTML elements
• Basic Attributes are defined by HTML BUT "value" kind of dynamic attributes (properties) which are like properties are defined and managed by DOM
• Attributes and properties are NOT the same
  
  • Attributes = HTML           |           Properties = DOM (Document Object Model)
• Attributes initialise DOM properties and then they are done - cannot change once they are initialised
• Property values however can change, HTML attribute value specifies initial value and the DOM value property is the current value

Syntax & Example: Property Binding is done with [square bracket] OR bind-properyName:

example: <input type="text" value="dinanath" />

• type in console:$0.getAttribute("value"); output:"dinanath"
• type in console:$0.value; output:"dinanath"
• Now type something new in text field "new Text"
• type in console:$0.getAttribute("value"); output:"dinanath"
• type in console:$0.value; output:"new Text"

• Note: Attribute does not changed but value property changed

• Property Binding done with [ ] square bracket also with {{ interpolation }} But its advisable to use [ ] as its supports string, boolean all property types, boolean value like true/false etc does not works well with {{ interpolation }}

Syntax & Example: component-demo5-propertybinding.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo5-propertybinding',
  templateUrl: './component-demo5-propertybinding.component.html',
  styleUrls: ['./component-demo5-propertybinding.component.css']
})
export class ComponentDemo5PropertybindingComponent implements OnInit {
  public _id = 'id1';
  public _isDisabled1 = true;
  public _isDisabled2 = false;

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo5-propertybinding.component.html

<div>
  <h1>component-demo5-propertybinding works!</h1>

  <h3>attributes vs value</h3>
  <input size="40" type="text" value="angular property binding" />

  <h3 ngNonBindable>property binding [ ] vs interpolation {{ ngNonBindable }} </h3>

  <input type="text" [id]="_id" value="[ ] property-binding" /><br />
  <input type="text" id="{{_id}}" value="{ } interpolation property-binding" /> <br /> <br />

  <h3>attribute boolean (property) interpolation does not support </h3>
  <input type="text" disabled="false" [id]="_id" value="boolean false not works" /><br />
  <input type="text" disabled="true" [id]="_id" value="boolean true not works" /> <br /> <br />

  <h3>property binding boolean values supported  </h3>
  <input type="text" [disabled]="false" [id]="_id" value="[property-binding] works" /><br />
  <input type="text" [disabled]="true" [id]="_id" value="[property-binding] works" /><br /> <br />

  <h3>property binding boolean property with variable </h3>
  <input type="text" [disabled]="_isDisabled1" [id]="_id" value="[ var ] disabled works" /><br />
  <input type="text" [disabled]="_isDisabled2" [id]="_id" value="[ var ] enabled works" /><br />

  <h3>property binding with bind- </h3>
  <input type="text" bind-disabled="_isDisabled1" [id]="_id" value="[ var ] disabled works" /><br />
  <input type="text" bind-disabled="_isDisabled2" [id]="_id" value="[ var ] enabled works" /><br />

</div>

   

    Image - Output - Property binding with {{}}, [ ] and bind-

07 Class Binding

• Class binding refers to applying different classes normally or depends on condition (dynamically)
• Class binding is very important and really useful as it allows developer to apply/add and remove classes to html element dynamically based on condition or user interaction
• Class Binding Syntax: <tag [class]="varName" />, here varName holds css className
• If [class] binding and class=" " attribute both present in tag, [class] binding get first/higher priority and class=" " attribute becomes null & void (class style properties not applied to text - so its advisable to use any one either class binding or class attribute)
• [ngClass] directive/attribute helps to apply multiple classes conditionally <tag [ngClass]="varObjectName"

Syntax & Example: styles.css (write css classes in any file)

.text-primary {
  color: blue;
}

.text-danger {
  color: red;
}

.text-success {
  color: lawngreen;
}

.text-special {
  font-weight:bold;
  font-style: italic;
  color:orchid;
}

.text-strikethrough {
  text-decoration: line-through;
}

.text-orange {
  color: orange;
}

Syntax & Example: component-demo6-classbinding.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo6-classbinding',
  templateUrl: './component-demo6-classbinding.component.html',
  styleUrls: ['./component-demo6-classbinding.component.css']
})
export class ComponentDemo6ClassbindingComponent implements OnInit {
  public successClass = 'text-success';
  public dangerClass = 'text-danger';
  public isSpecialClass = true;
  public isErrorClass = true;

  public messageClasses = {
    'text-primary': this.isSpecialClass,
    'text-strikethrough': this.isSpecialClass
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo6-classbinding.component.html

<div>
  <h1>component-demo6-classbinding works! </h1>

  <h3 ngNonBindable>[class]="varName" (varName holds css className present in css)</h3>

  <h4 class="text-orange">simple class attribute</h4>
  
  <h4 [class]="successClass">This is class binding with []</h4>

  <h4 class="{{successClass}}">This is class binding with interpolation</h4>

  <h4 [class]="successClass" class="text-orange">This is class binding with [] also class attribute</h4>

  <h4 [class.text-special]="isSpecialClass">This is class binding with boolean variable condition </h4>

  <h4 [class.text-danger]="isErrorClass">This is class binding with boolean variable condition </h4>

  <h4 [ngClass]="messageClasses">This is ngClass binding to deal with multiple classes at once</h4>
  
</div>

   

    Image - Output - Class binding with {{}}, [ ] and ngClass

08 Style Binding

• Style binding is similar to class binding but it refers to applying different inline styles to html element instead of applying css classes
• Style Binding Syntax:

<tag [style.color]="'orange'"> text </tag> 
OR 
<tag [style.color]="'varName'"> text </tag>

• [ngStyle] directive/attribute helps to apply multiple inline styles <tag [ngStyle]="varObjectName"

Syntax & Example: component-demo7-stylebinding.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo7-stylebinding',
  templateUrl: './component-demo7-stylebinding.component.html',
  styleUrls: ['./component-demo7-stylebinding.component.css']
})
export class ComponentDemo7StylebindingComponent implements OnInit {
  public greenColor = 'green';
  public redColor = 'red';
  public orangeColor = 'orange';
  public hasError = true;

  public headerStyles = {
    color: 'blue',
    textDecoration: 'line-through',
    fontStyle: 'italic'
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo7-stylebinding.component.html

<div>
  <h1>component-demo7-stylebinding works!</h1>

  <h3 ngNonBindable> &lt;tag [style.color]="'orange'"&gt; text &lt;/tag&gt;</h3>
  <h4 [style.color]="'orange'">applying inline styles</h4>

  <h3 ngNonBindable> &lt;tag [style.color]="'varName'"&gt; text &lt;/tag&gt;</h3>
  <h4 [style.color]="greenColor">applying inline styles with variable </h4>

  <h3 ngNonBindable> &lt;style.color]="hasError ? 'red' : 'green' "&gt; text &lt;/tag&gt;</h3>
  <h4 [style.color]="hasError ? 'red' : 'green' ">applying inline styles with variable conditions</h4>

  <h4 [ngStyle]="headerStyles">applying multiple inline styles</h4>
</div>

   

    Image - Output - Style binding with [style.] and [ngStyle]

09 Event Binding

• Event binding captures any DOM event and performs actions
• Angular provides an ability to bind the events along with the methods, Event binding is used with parenthesis ()
• Usually data binding done from Component Class .ts to Component Template .html (variables in class .ts files used/bind with html/template .html)
• To responds to user events like mouse clicks or keyboard events we need data flow from TEMPLATE to CLASS, event binding flows from TEMPLATE to CLASS (.HTML/TEMPLATE/VIEW to .TS/CLASS file)
• Syntax: <h1 (click)="fn()">Click Me - Change Style</h1>

Syntax & Example: component-demo8-eventbinding.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo8-eventbinding',
  templateUrl: './component-demo8-eventbinding.component.html',
  styleUrls: ['./component-demo8-eventbinding.component.css']
})
export class ComponentDemo8EventbindingComponent implements OnInit {
  public isButtonClicked = false;
  public greetingMessage = '';
  public eventType = '';
  // public withoutHandlerMessage = '';

  fn_changeStyles() {
    this.isButtonClicked = !this.isButtonClicked;
    this.greetingMessage = 'welcome to event binding';
  }

  fn_checkClick(evt) {
    console.log(evt);
    this.eventType = evt.type;
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo8-eventbinding.component.html

<div>
  <h1>component-demo8-eventbinding works!</h1>

  <h2>Event Binding</h2>

  <h1 (click)="fn_changeStyles()" [class.text-primary]="isButtonClicked" style="cursor:pointer;">Click Me - Change Style</h1>

  <div>isButtonClicked: {{isButtonClicked}}.  | {{isButtonClicked ? greetingMessage : " "}} </div> <br /><br />

  <button (click)="fn_checkClick($event)">Click me!</button> Event: {{eventType}} 

  <button (click)="withoutHandlerMessage = 'Without handler function' ">Without handler function - Click me!</button> {{withoutHandlerMessage}}

</div>

   

    Image - Event binding with (click)

   

    Image - Output - Event binding with (click) - After Click

10 Template Reference Variables

• When there is a user interaction we may want some data to flow from VIEW/TEMPLATE (.HTML) to the class .TS) to perform some operation
  • Example: value from input fields to perform some validation etc
• To easily access DOM elements and their properties, Template Reference Variables is used
• Template Reference Variables is created with #hash symbol followed by var name i.e. #heading1
• Syntax: <h1 #heading1>I am heading 1</h1>, here #heading1 is Template Reference Variable (a dynamic name/id) assigned to h1 tag

Syntax & Example: component-demo9-templaterefvars.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo9-templaterefvars',
  templateUrl: './component-demo9-templaterefvars.component.html',
  styleUrls: ['./component-demo9-templaterefvars.component.css']
})
export class ComponentDemo9TemplaterefvarsComponent implements OnInit {
  logDetails(_value) {
    console.log(_value);
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo9-templaterefvars.component.html

<div>
  <h1>component-demo9-templaterefvars works!</h1>

  <h2>Template Reference Variables</h2>
 
  <input #textInput type="text" placeholder="Enter Name" /> &nbsp; &nbsp;

  <button (click)="logDetails(textInput)">Get Input Field</button> &nbsp; &nbsp;

  <button (click)="logDetails(textInput.value)">Get Value of field </button> &nbsp; &nbsp;

</div>

   

    Image - Output - Template Reference Variables

11 Two Way Data Binding

• Data binding is one of the most powerful features of Angular, used widely for communication between TypeScript code (.ts - business logic) and different components (.html - view/template) shown to the users
• Whenever we work with Input Form fields its necessary/essentials that MODEL (data) and VIEW (template) both syncs well (any changes into HTML field should update the model/property and any updates/changes in model/property/variable than view should reflect those updated values)
• There are two types of data binding:
  1. One way data binding
  2. Two way data binding

11.1. One way data binding

• One way data binding is a simple/normal one way communication where HTML template is changed when any changes to TypeScript code/model/data/variable
• In one way data binding value of Model is used in the View (HTML) but we can't update Model from the View (.HTML Template)
• Example: Interpolation / String Interpolation, Property Binding, and Event Binding
• One way data binding works from class .ts file to template/view .html file:

Syntax & Example: component-demo10-onewaydatabinding.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo10-onewaydatabinding',
  templateUrl: './component-demo10-onewaydatabinding.component.html',
  styleUrls: ['./component-demo10-onewaydatabinding.component.css']
})
export class ComponentDemo10OnewaydatabindingComponent implements OnInit {
  public inputResultValue = 'One Way Data Binding!';

  public userNameText = 'Angular 7';

  public changeInputText(evt) {
    console.log(evt);
    this.userNameText = evt.target.value;
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo10-onewaydatabinding.component.html

<div>
  <h1>component-demo10-onewaydatabinding works!</h1>

  <h2>One way data binding</h2>
  One way data binding works from class .ts file to template/view .html file: <br /> <br />
  <input type="text" value={{inputResultValue}} /> <br />
  <input type="text" [value]=inputResultValue /> <br />
  <input type="text" bind-value=inputResultValue /> <br />

  <h2>One Way Data Binding works as Two way (work around)</h2>
  <input type="text" placeholder="Enter Name" [value]="userNameText" (input)="changeInputText($event)" /> &nbsp;&nbsp;
  <span><em><strong>{{userNameText}}</strong></em></span>
  
</div>

   

    Image - Simple one way data binding with {{}}, [ ] and bind-

   

    Image - Output - Simple one way data binding with {{}}, [ ] and bind-, used as two way data binding

11.2. Two way data binding

• Two Way Data Binding helps to update the property at the same time displays the value of the property
• In two way data binding, automatic synchronization of data happens between the Model and the View
• Here whenever we make changes in the Model(data/variable) it will be reflected in the View and when you make changes in View(HTML/template) it will be reflected in Model
• "ngModel" Directive is used to implement Two Way Data Binding (basically VIEW & MODEL should always be sync)
• [ ] square bracket/property binding is used for data flow from class to the template and ( ) parentheses/event binding for data from template to class
• [(ngModel)] - this syntax is known as [(banana in the box)]
• To use [(ngModel)] Directive we must need to import FormsModule from @angular/forms and also add to imports array in app.module.ts: import { FormsModule } from '@angular/forms';

• Note: In two way data binding value flow from an Input Text field to the class file and then to view/template file

Syntax & Example: app.module.ts

// import forms module for two way data binding
import { FormsModule } from '@angular/forms';

imports: [
    BrowserModule,
    FormsModule
  ],

Syntax & Example: component-demo11-twowaydatabinding.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo11-twowaydatabinding',
  templateUrl: './component-demo11-twowaydatabinding.component.html',
  styleUrls: ['./component-demo11-twowaydatabinding.component.css']
})
export class ComponentDemo11TwowaydatabindingComponent implements OnInit {
  public nameText = 'Angular 6';
  
  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo11-twowaydatabinding.component.html

<div>
  <h1>component-demo11-twowaydatabinding works!</h1>

  <h2>Two way data binding</h2>
  
  <input type="text" [(ngModel)]="nameText" placeholder="Enter Name"/> {{nameText}}
  
</div>

   

    Image - Output - Two way data binding with [(ngModel)], FormsModule

12 ngIf Directive

• Directives are an instructions in the DOM, they specify how to place your components and business logic in the Angular
• Directives are js class and declared as @directive
• There are 3 main types of directives in Angular:
  1. Component Directives - Component directives are used in main class (app.component.ts). They contain the detail of how the component should be processed, instantiated and used at runtime
  2. Structural Directives - Structural Directives let us Add or Remove (Show or Hide) HTML elements from DOM. Structural directives start with a * sign. These directives are used to manipulate and change the structure of the DOM elements. For example, *ngIf and *ngFor etc.
  3. Attribute Directives - Attribute directives look like a normal HTML Attribute and mainly used in databinding and event binding. Attribute directives are used to change the look and behavior of the DOM elements. Attribute Directives affect only the element they are added to. For example: ngClass, ngStyle etc.
• Most important/widely used inbuilt Structural directives are:
  • ngIf - conditionally render/show-hide html elements
  • ngSwitch - conditionally render/show-hide html elements
  • ngFor - render/show list of html elements through loop

*ngIf

• *ngIf directive is used to change the output conditionally
• If the condition is false, the DOM element does not render
• With *ngIf use truthy or falsy value which conditionally renders the DOM elements
• ng-template is like a container for chunks/group of HTML elements controlled once

Syntax & Example: component-demo12-ngif.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo12-ngif',
  templateUrl: './component-demo12-ngif.component.html',
  styleUrls: ['./component-demo12-ngif.component.css']
})
export class ComponentDemo12NgifComponent implements OnInit {
  public isShow=true;
  public hasDisplay=false;

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo12-ngif.component.html

<div>
  <h1>component-demo12-ngif works!</h1>

  <h2>*ngIf</h2>
  
  <ul>
    <li *ngIf="true">Show me </li>
    <li *ngIf="false">I am NOT rendered in DOM </li>
    <li *ngIf="isShow">Please show me - conditional variable/property from class</li>
  </ul>

  <h2>ngIf else ng-template</h2>
  If condition is false, different DOM element renders as specified in "ng-template else">

  <!-- variable true - show me, else show other ng-template -->
  <div *ngIf="hasDisplay; else elseTemplate">
    <h5>I have used in ngIf TRUE part</h5>
  </div>

  <ng-template #elseTemplate>
    <h5>I am using ngIf FALSE/ELSE part in ng-template</h5>
  </ng-template>

  <h2>ngIf - ng-template else ng-template</h2>
  depends on variable/condition show ng-template1 else show other ng-template2

  <!-- variable true then show ng-template1 else show other ng-template2 -->
  <div *ngIf="hasDisplay; then trueTemplate; else falseTemplate"></div>

  <ng-template #trueTemplate>
    <h5>I am #trueTemplate</h5>
  </ng-template>

  <ng-template #falseTemplate>
    <h5>I am #falseTemplate</h5>
  </ng-template>

</div>

   

    Image - Output - *ngIf - Structural directive to control/add/remove elements to DOM conditionally

13 ngSwitch Directive

• ngSwitch directive is similar to other programming languages swtich statement, only the difference is with angular we render HTML elements instead of executing logics

Syntax & Example: component-demo13-ngswitch.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo13-ngswitch',
  templateUrl: './component-demo13-ngswitch.component.html',
  styleUrls: ['./component-demo13-ngswitch.component.css']
})
export class ComponentDemo13NgswitchComponent implements OnInit {
  public curColor='red';
  // public curColor='green';
  // public curColor = 'blue';

  // public curColor = 'black';

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo13-ngswitch.component.html

<div>
  <h1>component-demo13-ngswitch works!</h1>

  <h2>*ngSwtich</h2>

  <div [ngSwitch]="curColor">
    <div *ngSwitchCase="'red'" [style.color]="curColor">RED | {{curColor}} | color</div>
    <div *ngSwitchCase="'green'" [style.color]="curColor">GREEN | {{curColor}} | color</div>
    <div *ngSwitchCase="'blue'" [style.color]="curColor">BLUE | {{curColor}} | color</div>
    <div *ngSwitchDefault>Default BLACK</div>
  </div>

</div>

   

    Image - Output - *ngSwitch - Structural directive to control/add/remove elements to DOM conditionally

14 ngFor Directive

• ngFor directive is similar to other programming languages for loop statement, only the difference is with angular we render the list of HTML elements instead of executing logics

Syntax & Example: component-demo14-ngfor.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo14-ngfor',
  templateUrl: './component-demo14-ngfor.component.html',
  styleUrls: ['./component-demo14-ngfor.component.css']
})
export class ComponentDemo14NgforComponent implements OnInit {
  // public arrColors = ['red', 'green', 'blue','cyan','magenta','black'];
  public arrColors = ['red', 'green', 'blue'];

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo14-ngfor.component.html

<div>
  <h1>component-demo14-ngfor works!</h1>

  <h2>*ngFor</h2>

  <h2>*ngFor Basics </h2>
  <ul>
    <li *ngFor="let color of arrColors" [style.color]="color">
      {{color}}
    </li>
  </ul>

  <h2>*ngFor with id and class </h2>
  <ul>
    <li *ngFor="let color of arrColors;" id="{{color}}" class="{{color}}" [style.color]="color">
      {{color}}
    </li>
  </ul>

  <h2>*ngFor with index </h2>
  <ul>
    <li *ngFor="let color of arrColors; index as curIndex" id="{{color}}" class="{{color}}" [style.color]="color">
      Index is: {{curIndex + 1 }}. {{color}}
    </li>
  </ul>

  <h2>*ngFor with index - first / last / even / odd </h2>
  <ul>
    <li *ngFor="let color of arrColors; index as curIndex; first as firstIndex; last as lastIndex; even as evenIndex; odd as oddIndex" id="{{color}}" class="{{color}}" [style.color]="color">
      {{curIndex}}. {{color}}  :--:  First Item: {{firstIndex}}  :--: Last Item: {{lastIndex}}  :--:  Odd: {{oddIndex}} :--:  Even: {{evenIndex}} :--:
    </li>
  </ul>

</div>

   

    Image - Output - *ngFor - Structural directive to render/loop html elements from an array/object

15 Component Interaction

• Component interact [parent to child and vice versa] with @input() & @output() decorator
  • @input() decorator - Parent component sends data, Child component accepts with @input() decorator (parent to child component communication with @input() decorator)
  • @output() decorator - Child component sends data/events, Parent component accepts with @output() decorator (child to parent component communication with @output() decorator)
• To send data from Child to Parent we need events i.e. create Events-EventEmitter

15.1. Parent to child communication with @Input() decorator:

1. Parent class/.ts file - Create a property or class member/variable, example: parentMessage = 'From Parent';
2. Parent view/.html file - In child selector tag use parent variable with property binding for communication, example: <app-component-demo15-childparent [parentData]="parentMessage"></app-component-demo15-childparent>
3. Child component class/.ts file - Receive data data/value coming from parent component, example: @Input() public parentData;
4. Child view/.html file - Bind / Get Parent Data in Child component example: Hello <strong>{{parentData}}</strong>

Syntax & Example: parent component - app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  // create a property to send from parent to child
  parentMessage = 'From Parent';
    
}

Syntax & Example: parent component - app.component.html

<!-- component interaction - parent to child and child to parent communication -->

<!-- send property from parent to child - include in child element component selector -->
<app-component-demo15-childparent [parentData]="parentMessage"></app-component-demo15-childparent>

Syntax & Example: child component - component-demo15-childparent.component.ts

import { Component, OnInit, Input, Output, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-component-demo15-childparent',
  templateUrl: './component-demo15-childparent.component.html',
  styleUrls: ['./component-demo15-childparent.component.css']
})
export class ComponentDemo15ChildparentComponent implements OnInit {
  // parent to child 

  // receive data data/value coming from parent component
  @Input() public parentData;
  // @Input() public parentName;

  // alias based method
  // @Input('parentData') public parentName;

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: child component - component-demo15-childparent.component.html

<div>
  <h1>component-demo15-childparent works!</h1>

  <!-- parent to child -->

  <u>Bind / Get Parent Data in Child component</u>:
  Hello <strong>{{parentData}}</strong> <br /> <br /> <br />

  <!-- <u>bind / Get Parent Data in Child alias based method</u>:
  Hello <strong>{{parentName}}</strong> <br /><br /> -->
  
</div>

   

    Image - Output - component communication parent to child with input decorator

15.2. Child to parent communication with @Ouput() decorator:

1. Child component class/.ts file - Create child output event to send to parent by using EventEmitter class
2. Child component class/.ts file - Create child event handler function and emit some events/message
3. Child view/.html file - Create a button element to fire child event handler function
4. Parent view/.html file - In child selector tag capture child event, example: <app-component-demo15-childparent (childEvent)="messageChild=($event)"></app-component-demo15-childparent>
5. Parent view/.html file - Bind the messageChild property in view <u>Parent component showing message from child component</u>: <strong>{{messageChild}}</strong>

Syntax & Example: child component - component-demo15-childparent.component.ts

import { Component, OnInit, Input, Output, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-component-demo15-childparent',
  templateUrl: './component-demo15-childparent.component.html',
  styleUrls: ['./component-demo15-childparent.component.css']
})
export class ComponentDemo15ChildparentComponent implements OnInit {
  // parent to child 

  // receive data data/value coming from parent component
  @Input() public parentData;
  // @Input() public parentName;

  // alias based method
  // @Input('parentData') public parentName;

  // child to parent

  // create child event to send to parent
  @Output() public childEvent = new EventEmitter();

  // child event handler function
  childFireEvent() {
    this.childEvent.emit("Message from Child to Parent");
  }

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: child component - component-demo15-childparent.component.html

<div>
    <h1>component-demo15-childparent works!</h1>
    <!-- child to parent -->

    <!-- Fire child event on button click -->
    <button (click)="childFireEvent()">Send Child Event to Parent</button>
</div>

Syntax & Example: parent component - app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  // create a property to send from parent to child
  parentMessage = 'From Parent';
  
  // child to parent
  messageChild;
}

Syntax & Example: parent component - app.component.html

<!-- component interaction - parent to child and child to parent communication -->

<!-- send property from parent to child - include in child element component selector -->
<app-component-demo15-childparent [parentData]="parentMessage" (childEvent)="messageChild=($event)"></app-component-demo15-childparent>

   

    Image - Output - component communication child to parent with ouput decorator

16 Pipes

• Pipes (Filters) helps to transform data before displaying to view
• Pipes (Filters) can be added in AngularJS to format data
• Pipes (Filters) is denoted by piping | symbol
• There are many built-in/default pipes available in angular like: String related pipes (uppercase, lowercase), Number related pipes (number), Currency pipes, Date pipes, JSON pipes.
• We can also create custom pipes as per out requirements with Pipe, PipeTransform class & transform method

Syntax & Example: component-demo16-pipesfilters.component.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-component-demo16-pipesfilters',
  templateUrl: './component-demo16-pipesfilters.component.html',
  styleUrls: ['./component-demo16-pipesfilters.component.css']
})
export class ComponentDemo16PipesfiltersComponent implements OnInit {
  public nameText = 'Angular js';
  public messageText = 'Welcome to Angularjs';
  public greetingText = 'angular 2/4/5/6 is component based';

  public objTechnology = {
    'firstName': 'angular',
    'lastName': 'js',
    'version': 6.0
  }

  public number1 = 5.786;

  public currentDate = Date();

  constructor() { }

  ngOnInit() {
  }

}

Syntax & Example: component-demo16-pipesfilters.component.html

<div>
  <h1>component-demo16-pipesfilters works!</h1>

  <h2>pipes</h2>
  
  <h2>String based Pipes : Format string</h2>
  uppercase: {{ nameText | uppercase }} <br />
  lowercase: {{ messageText | lowercase }} <br />
  titlecase: {{ greetingText | titlecase }} <br />

  slice:start:end (not including that letter): {{ greetingText | slice:8}} <br />
  <!-- slice:starting point:limit/up to (not including that letter) -->
  slice:start:end (not including that letter): {{ greetingText | slice:14:15}} <br />

  <h2>JSON Pipes - Shows json representation of an object</h2>
  json: {{ objTechnology | json }} <br />

  <h2>Number Pipes - Format Number, Integers</h2>
  <!-- min integer digit. min decimal digit - max decimal digit. -->
  number (min integer digit. min decimal digit - max decimal digit): {{ 5.29898 | number:"1.2-3" }} <br />
  number (min integer digit. min decimal digit - max decimal digit): {{ 5.29898 | number:"2.2-2" }} <br />

  percent: {{ 0.29898 | percent }} <br />

  <h2>Currency Pipes - Transform Currency values</h2>
  currency: {{ 0.29898 | currency }}<br />
  currency: {{ 0.29898 | currency:'Rs.' }} <br />
  currency: {{ 0.29898 | currency:'GBP' }} <br />
  currency: {{ 0.29898 | currency:'GBP':'code' }} <br />

  <h2>Date Pipes - Transform Date</h2>
  Date: {{ currentDate }}<br />

  date:short: {{ currentDate | date:'short' }}<br />
  date:shortDate: {{ currentDate | date:'shortDate' }}<br />
  date:shortTime: {{ currentDate | date:'shortTime' }} <br /> <br />

  date:medium: {{ currentDate | date:'medium' }}<br />
  date:mediumDate: {{ currentDate | date:'mediumDate' }}<br />
  date:mediumTime: {{ currentDate | date:'mediumTime' }}<br /> <br />

  date:long: {{ currentDate | date:'long' }}<br />
  date:longDate: {{ currentDate | date:'longDate' }}<br />
  date:longTime: {{ currentDate | date:'longTime' }}<br /> <br />

</div>

   

    Image - Output - Transform/Format data with pipes

17 Services

• Programming Principles:
  • DRY - Do not repeat yourself (DRY) - Avoid making copies of data in different files. (example: List & Details components using same employee object created twice in respective class file)
  • SRP - Single Responsibility Principles (one class/function should perform one task/responsibility)
  • KISS - Keep It Simple Stupid!
• Service is a class with a specific purpose and widely used to:
  • Share data - Between multiple pages/components
  • Implement application logic - Calculations, Repeatative tasks/functionalities etc.
  • External Interaction - Database connectivity
• Services are a great and awesome way to share information among multiple classes/components, just create a service and inject it in respective classes/components

18 Dependency Injection DI

• Drawback of code without Dependency Injection (DI):
  • Code is not flexible
  • If main code (dependencies) changed we need to check and change our code
  • Code is not suitable for testing
• Dependency Injection (DI) as a design pattern
  • Dependency Injection DI is a coding pattern/standard in which a class receives its required dependencies from external sources rather than creating them itself to avoid tight coupling
• Dependency Injection (DI) as a Framework - Register all dependencies with Injector a central place/container
  • 3 steps involved to create and use service in angular:
    1. Define the Service class
    2. Register with Injector
    3. Declare as a dependency in List and Details both component
• @Injectable() decorator tells angular that this service might itself have injected dependencies

19 Using a Service

• 3 steps involved to create and use service in angular:
  1. Define the Service class
  2. Register with Injector
  3. Declare as a dependency in List and Details both component  

1.Define the Service class

1. Create service (which is responsible for providing employee data) with the command "ng g s employee" OR "ng generate service employee"

Syntax & Example: employee.service.ts

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class EmployeeService {
  // 1.1. create a new method which holds employee data
  getEmployees() {
    return [
      { 'id': 1, 'name': 'Amitabh', 'age': 75, 'city': 'Alahabad' },
      { 'id': 2, 'name': 'Akshay', 'age': 55, 'city': 'Delhi' },
      { 'id': 3, 'name': 'RajaniKanth', 'age': 73, 'city': 'Chennai' },
      { 'id': 4, 'name': 'Rajesh Khanna', 'age': 85, 'city': 'Kolkatta' }
    ]
  }

  constructor() { }

}

2.Register with Injector

2. Register with Injector in app module file 'app.module.ts'

Syntax & Example: app.module.ts

// 2.1. import custom created service to Register with Injector
import { EmployeeService } from './services/employee.service';

// 2.2. import service in providers its compulsion to insert services in the provider's array
providers: [ EmployeeService ]

3.Declare as a dependency in both List and Details component

3. import service in necessary component files - Declare as dependency in constructor employee-list.component.ts & employee-details.component.ts

Syntax & Example: component-demo191-serviceemployeelist.component.ts & component-demo192-serviceemployeedetails.component.ts

import { Component, OnInit } from '@angular/core';

// 3.1. import service in necessary component files - Declared as dependency
import { EmployeeService } from '../../services/employee.service';

@Component({
  selector: 'app-component-demo191-serviceemployeelist',
  templateUrl: './component-demo191-serviceemployeelist.component.html',
  styleUrls: ['./component-demo191-serviceemployeelist.component.css']
})
export class ComponentDemo191ServiceemployeelistComponent implements OnInit {
  // 3.3. define an empty local employees array which will hold employees data after service all
  public employees = [];

  // 3.2. refer to service with local variable as dependency in constructor
  constructor(private employeeService: EmployeeService) { }

  ngOnInit() {
    // 3.4. on component initialization get values from service method
    this.employees = this.employeeService.getEmployees();
  }

}

4.Add Markup and bind required data in template/view - employee-list.component.html (component-demo191-serviceemployeelist.component.html) file:

Syntax & Example:

<h2>Employee list:</h2>
<ul>
    <li *ngFor="let employee of employees">
        {{employee.id}} {{employee.name}} 
    </li>
</ul>

5.Add Markup and bind required data in template/view - employee-details.component.html file: component-demo192-serviceemployeedetails.component.html

Syntax & Example:

<div>
  <h1>component-demo192-serviceemployeedetails works!</h1>

  <h2>Employee Details list:</h2>
  <ul>
    <li *ngFor="let employee of employees">
      {{employee.id}} {{employee.name}} {{employee.age}} {{employee.city}}
    </li>
  </ul>

</div>

   

    Image - Output - services and component folder structure

   

    Image - Output - single service used in multiple component as per logic and requirement

20 HTTP and Observables

• Http services are used to fetch the data from web server (instead of using hard coded data/json files)

20.1. Http Mechanism:

1. Send http request
2. Receive and process http response

Request:

Component file calls -> Service -> Get -> HTTP -> request -> server (DB)

Response:

Component file calls <- Service (cast data) <- Observable <- HTTP <- response <- server (DB)

Observables:

The response/results/returns which we get from the HTTP call is nothing but an Observables. The service needs to cast Observables into an Array/Object and then pass to the required components.

20.2. What exactly are Observables?

• A sequence of data/items that arrive asynchronously over time
• HTTP Call = Single item and Single item = HTTP response
• Observables are HTTP response which arrives asynchronously

20.3. HTTP, Observables, and RxJS:

• 4 steps to fetch data from HTTP & observables:
  1. HTTP Get request from service
  2. Receive the observable and cast it into an array/Object
  3. Subscribe to the observable from List and Details component class
  4. Assign the received array/Object to a local variable

20.4. RxJS

• Reactive Extensions for JavaScript
• External library to work with Observables
• No-where related to ReactJS library from Facebook

21 Fetch Data Using HTTP and Observables

• Http & HttpClientModule:
• Till Angular 4 - Http module used
• In Angular 5 - HttpClientModule used (HttpClientModule provides simplified APIs to work with http functionality)
• We know an Observables are return as result of a http call, to handle an exceptions on observables we make a use of 'catch' operator
  
  
• 4 steps to fetch data from http & observables:
  1. HTTP Get request from service
  2. Receive the observable and cast it into an array/Object
  3. Subscribe to the observable from List and Details component class
  4. Assign the received array/Object to local variable
• create a custom service to handle http data with command: ng g s employeeHttp

1.HTTP Get request from service

Syntax & Example: 1. app.module.ts

 // import HttpClientModule and add to imports array
    // 1a. import HttpClientModule
    import { HttpClientModule } from '@angular/common/http'

    // 1b. add to imports array
    imports: [
        BrowserModule,
        BrowserAnimationsModule,
        FormsModule,
        HttpClientModule
    ],
     
    // 1c. import custom created service Register with Injector
    import { EmployeeHttpService } from './employee-http.service';

    // import service in providers
    providers: [EmployeeService, EmployeeHttpService],

2.Receive the observable and cast it into an array/Object

Syntax & Example: 2. employee-http.service.ts

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import { IEmployee } from '../models/iemployee';

@Injectable({
  providedIn: 'root'
})
export class EmployeehttpService {
  // 2c. create json data file
  private jsonUrl:string= "/assets/data/employees.json";

  // 2a. create local variable for HttpClient as DI
  constructor(private httpClient: HttpClient) { }

  // 2b. http get
  getEmployees(): Observable<IEmployee[]> {
    return this.httpClient.get<IEmployee[]>(this.jsonUrl);
  }
  
}

/* 
// 2a. create local variable for HttpClient as DI
    constructor(private _HttpClient:HttpClient) { }

    import { HttpClient } from '@angular/common/http';

    // 2b. in a getEmployees method make get request
    // getEmployees(){
    //   return this._HttpClient.get(_jsonUrl);
    // }

    // 2b. http get
    getEmployees():Observable<IEmployee[]>{
        return this._HttpClient.get<IEmployee[]>(this._jsonUrl);
    }

    // 2c. create json data file
    private _jsonUrl:string= "/assets/data/employees.json";

    // import model/interface file
    import { IEmployee } from './employee-model-interface';
    import { Observable } from 'rxjs/Observable';
*/

Syntax & Example: 3. ceate employees.json data file inside assets/data folder

[
    { "id": 1, "name": "Amitabh", "age": 75, "city": "Alahabad" },
    { "id": 2, "name": "Akshay", "age": 55, "city": "Delhi" },
    { "id": 3, "name": "RajaniKanth", "age": 73, "city": "Chennai" },
    { "id": 4, "name": "Rajesh Khanna", "age": 85, "city": "Kolkatta" }
]

[
    {"id":1, "name":"Ratan Tata", "age":75},
    {"id":2, "name":"Adi Godrej", "age":65},
    {"id":3, "name":"K M Birla", "age":55},
    {"id":4, "name":"Laxmi Mittal", "age":58},
    {"id":5, "name":"Chanda Kochar", "age":50},
    {"id":6, "name":"Amitabh B", "age":76}
]

Syntax & Example: 4. create IEmployee.ts an employee model/interface file to store exact data types and rules

export interface IEmployee {
    id:number;
    name:string;
    age:number
}

3.Subscribe to the observable from List and Details component class
4.Assign the received array/Object to local variable

Syntax & Example: 3. employee-http-list.component.ts

import { Component, OnInit } from '@angular/core';
import { EmployeehttpService } from '../services/employeehttp.service';

@Component({
  selector: 'app-component-demo211-httpemployeelist',
  templateUrl: './component-demo211-httpemployeelist.component.html',
  styleUrls: ['./component-demo211-httpemployeelist.component.css']
})
export class ComponentDemo211HttpemployeelistComponent implements OnInit {
  public employees = [];

  constructor(private employeehttpService: EmployeehttpService) { }

  ngOnInit() {
    // on component initialization get value from http subscribe
    // data =>: argument of the function
    // this.employees = data: body of the function
    // subscribe: to receive data
    this.employeehttpService.getEmployees().subscribe(data => this.employees = data)
  }

}

Syntax & Example: component-demo211-httpemployeelist.component.html

<div>
  <h1>component-demo211-httpemployeelist works!</h1>

  <h2>HTTP Services and Observables</h2>

  <h2>Employee HTTP Observables list:</h2>
  <ul>
    <li *ngFor="let employee of employees">
      {{employee.id}} {{employee.name}}
    </li>
  </ul>

</div>

Syntax & Example: component-demo212-httpemployee-details.component.html

<div>
  <h1>component-demo212-httpemployee-details works!</h1>

  <h2>Employee HTTP Observables Details list:</h2>
  <ul>
    <li *ngFor="let employee of employees">
      {{employee.id}} {{employee.name}} {{employee.age}} {{employee.city}}
    </li>
  </ul>

</div>

   

    Image - Output - http-observables services and component folder structure

   

    Image - Output - http-observables

22 Creating Custom Directives

• We know that Directives are an instructions in the DOM, they specify how to place your components and business logic in the Angular
• There are many inbuilt structural directives like ngIf, ngSwitch and ngFor used widely in angular
• We can also create custom directives to implement some common logic/functionality (not existing) as a class declared as @directive

Let's create a custom attribute directive to highlight text with blue color & italic style

1. The command to create directive: ng generate directive name OR ng g directive name.
   1. In the current app, we want to create all custom directives under directives folder so use command as: ng generate directive directives/blueHighlight
   2. The above command will generate and update the following:

    CREATE src/app/directives/blue-highlight.directive.spec.ts (253 bytes)
    CREATE src/app/directives/blue-highlight.directive.ts (155 bytes)
    UPDATE src/app/app.module.ts (4690 bytes)

Syntax & Example: app.module.ts will be updated automatically with new directive entry

// 22. directives - import custom created directives
import { BlueHighlightDirective } from './directives/blue-highlight.directive';

declarations: [
    BlueHighlightDirective
],

2. Once directive created, in blue-highlight.directive.ts assign/change selector name from appBlueHighlight to "blueHighlight" or so.

   1. Open any component html file and use "blueHighlight" directive as a attribute (i am trying in app.component.html): <h1 blueHighlight> Hello World! I am custom directive </h1>
   2. To target, get or capture the current html element we can import and use ElementRef and nativeElement utilities

3. Directives called before the element is rendered so it's advisable to perform all content related actions inside ngOnInit() life cycle hook

Syntax & Example: blue-highlight.directive.ts

import { Directive, ElementRef } from '@angular/core';

@Directive({
  selector: '[blueHighlight]'
})
export class BlueHighlightDirective {

  constructor(private elem:ElementRef) { 
    console.log('current Element:', elem);
    // elem.nativeElement.innerText= 'Dynamic text innerHTML';
    elem.nativeElement.style.color = `#0000ff`;
    elem.nativeElement.style.fontStyle = 'italic';
    elem.nativeElement.style.backgroundColor   = '#c7c7ff';
  }

}

Syntax & Example: app.component.html

<!-- custom directive  -->
<h1> 22 Hello World! Lets learn custom directive </h1>

<li blueHighlight> I am custom directive </li>

<p>The command to create directive: <span blueHighlight>`ng generate directive blueHighlight`</span> OR <span blueHighlight>`ng g directive blueHighlight`</span>. In current app we want to create all custom directives under `directives` folder so use command as: <span blueHighlight>`ng generate directive directives/blueHighlight`</span>. Above command will Genreate and Update following: <br/>
<br/>
<span blueHighlight>CREATE</span> src/app/directives/blue-highlight.directive.spec.ts (253 bytes) <br/>
<span blueHighlight>CREATE</span> src/app/directives/blue-highlight.directive.ts (155 bytes) <br/>
<span blueHighlight>UPDATE</span> src/app/app.module.ts (4690 bytes) <br/>
</p>

   

    Image - Output - custom-directives folder structure

   

    Image - Output - custom-directives elementref nativelement

   

    Image - Output - custom-directives elementref nativelement style

23 Custom Directives with Events and HostListener

• In Angular, the @HostListener() function decorator allows you to handle events of the host element in the directive class
• @HostListener Decorator declares a DOM event to listen for, and provides a handler method to run when that event occurs
• Basic syntax of @Hostlistener is:
  • @Hostlistener('eventName',[args]) OR @Hostlistener('target:EVENT',[args])
  • eventName: The CSS event to listen for
  • args: A set of arguments to pass to the handler method when the event occurs

Let's create a custom attribute directive to highlight text and also have a click event

1. The command to create directive: ng generate directive name OR ng g directive name.
   1. In the current app, we want to create all custom directives under directives folder so use command as: ng generate directive directives/highlightClick
   2. The above command will generate and update the following:

    CREATE src/app/directives/highlight-cilck.directive.spec.ts (257 bytes)
    CREATE src/app/directives/highlight-cilck.directive.ts (157 bytes)
    UPDATE src/app/app.module.ts (4855 bytes)

Syntax & Example: app.module.ts will be updated automatically with new directive entry

/// 23. directives - import custom created directives
import { HighlightCilckDirective } from './directives/highlight-cilck.directive';

declarations: [
    HighlightCilckDirective
],

2. Once directive created, in highlight-cilck.directive.ts assign/change selector name from appHighlightCilck to "highlightCilck" or so.
   1. Open any component html file and use "highlightCilck" directive as a attribute (i am trying in app.component.html): <h1 highlightCilck> Hello World! I am custom directive with Click</h1>
   2. To target, get or capture the current html element we can import and use ElementRef and nativeElement with @HostListener utilities

Syntax & Example: blue-highlight.directive.ts

import { Directive, ElementRef, HostListener } from '@angular/core';

@Directive({
  selector: '[highlightCilck]'
})
export class HighlightCilckDirective {

  constructor(private elem: ElementRef) {
    console.log('current Element:', elem);
    // elem.nativeElement.innerText= 'Dynamic text innerHTML';
    elem.nativeElement.style.color = `#ff0000`;
    elem.nativeElement.style.backgroundColor = '#ffd5d5';
    elem.nativeElement.style.cursor = 'pointer';
  }

  // element click event - @Hostlistener('eventName',[args])
  @HostListener('click') showAlert() {
    window.alert('Custom Directive - @HostListener events!');
  }

  // use global objects like document/window click - @Hostlistener('target:EVENT',[args])
  // @HostListener('document:click', ['$event'])
  // showElementClicked(elem) {
  //   window.alert('Document Clicked');
  // }
}

Syntax & Example: app.component.html

<!-- custom directive with @HostListener -->
  <h1> 23 Hello World! Lets learn custom directive with click </h1>

  <li highlightCilck> I am custom directive </li>

  <p>The command to create directive: <span highlightCilck>`ng generate directive highlightCilck`</span> OR <span highlightCilck>`ng g directive highlightCilck`</span>. In current app we want to create all custom directives under `directives` folder so use command as: <span highlightCilck>`ng generate directive directives/highlightCilck`</span>. Above command will Genreate and Update following: <br/>
  <br/>
    <span highlightCilck>CREATE</span> src/app/directives/blue-highlight.directive.spec.ts (253 bytes) <br/>
    <span highlightCilck>CREATE</span> src/app/directives/blue-highlight.directive.ts (155 bytes) <br/>
    <span highlightCilck>UPDATE</span> src/app/app.module.ts (4690 bytes) <br/>
  </p>

   

    Image - Output - custom-directives events @hostlistener

24 Creating Custom Pipes

• We learnt that Pipes (Filters) helps to transform data before displaying to view, format the data
• There are many inbuilt pipes like uppercase, number, currency and date used widely in angular to transform data
• We can also create custom pipes as per our requirements with Pipe, PipeTransform class & transform method

Let's create a custom pipe to get the square root of the given number

1. Inside app/pipes folder create a new .ts file named squareRootPipe.ts
2. In squareRootPipe.ts to create a custom pipe we need to import Pipe, PipeTransform class from @angular/core and also use transform method
3. Also in the @Pipe directive we have to give the name to the current pipe, which will be used in the .html file, like name: 'squareRootPipe'
4. In app.module.ts file import and add in declarations squareRootPipe.ts as it's created manually

• To create a pipe using angular CLI:
  • syntax: ng generate pipe pipeName OR ng generate pipe path/pipeName
  • command: ng generate pipe pipes/reversText
• The above command will generate pipe reversTextPipe.ts with @Pipe decorator, implements PipeTransform and also update the src/app/app.module.ts with necessary imports entries

Syntax & Example: squareRootPipe.ts

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'squareRootPipe'
})

export class SquareRootPipe implements PipeTransform {
  transform(curValue: number): number {
    return Math.sqrt(curValue);
  }

}

Syntax & Example: app.module.ts

// 24. pipes - import custom created pipes
import { SquareRootPipe } from './pipes/squareRootPipe';

declarations: [
    SquareRootPipe
],

Syntax & Example: app.component.html

<!-- custom pipe  -->
<h1> 24 Lets learn custom pipe to format/transform data </h1>

<ul>
    <li>Square Root of 81 is: {{ 81 | squareRootPipe }}</li>
    <li>Square Root of 100 is: {{ 100 | squareRootPipe }}</li>
</ul>

   

    Image - Output - custom-pipes-filters folder structure

   

    Image - Output - custom-pipes, filters with pipe & pipeTransform