TypeScript Part 11(Tuple, Enum,Never)

Tuple

It is a new data type called Tuple. It can contains values of two different data types.

Example 

var empId: number = 1;

var empName: string = "Uday";        

// Using Tuple type variable we can combine above two variables into a single one as 

var employee: [number, string] = [1, "Uday"];

Tuple can include multiple data types as well. 

Example

var user: [number, string, boolean, number, string];// declare tuple variable

user = [1, "Uday", true, 20, "Admin"];// initialize tuple variable

Tuple Array

Example

var employee: [number, string][];

employee = [[1, "Uday"], [2, "Kumar"], [3, "Kittu"]];

How to access Tuple Elements

var employee: [number, string] = [1, "Uday"];

employee[0]; // returns 1

employee[1]; // returns "Uday"

Example

var user: [number, string, boolean, number, string];// declare tuple variable

user = [1, "Uday", true, 20, "Admin"]

console.log(user[0]);

console.log(user[1]);

console.log(user[2]);

console.log(user[3]);

Output

Add Elements to Tuple

var employee: [number, string] = [1, "Uday"];

employee.push(2, "Kumar"); 

console.log(employee); //Output: [1, 'Uday', 2, 'Kumar']

Example

var user: [number, string] = [1, "Uday"];

user.push(2, "Kumar");

console.log(employee);

console.log(user[0]);

console.log(user[1]);

Working with OnBlur and Focus Events

Blur: It specifies the actions to perform when element looses the focus.

Focus specifies the action to perform when element get focus.

Cut, Copy, Paste 

Specifies action to perform on cut, copy and paste functionality.

Example

Add a new component

ng g c eventsample6

ScreenShot

.ts changes

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

@Component({

  selector: 'app-eventsample6',

  templateUrl: './eventsample6.component.html',

  styleUrls: ['./eventsample6.component.css']

})

export class Eventsample6Component {

public txtName:any;

public msg:any;

public status:any;

public onBlur() {

  this.msg='';

  this.txtName=this.txtName.toUpperCase();

}

public onFocus()

{

  this.msg="Removed and Placed onto Clip Board";

}

public onCopy()

{

  this.status="Copied to ClipBoard";

}

public onPaste()

{

  this.status="Inserted from ClipBoard";

}

}

ScreenShot

.html changes

<div class="container">

    <h2>User Details</h2>

    Name:

    <input (focus)="onFocus()" (blur)="onBlur()"

    (copy)="onCopy()"

    (paste)="onPaste()" type="text"

    [(ngModel)]="txtName">

    <span> {{msg}}</span>

    <br/>

    <div class="text-center">

        {{status}}

    </div>

</div>

Next make changes on appmodule.ts and Index.html as shown in the previous examples

Output

Working with Change Event Binding

 It specifies  action to perform when the value is changed in any element dynamically .It is mostly used with Range Numbers, Select Element

Example

ng g c eventsample4

.Ts File Changes

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

@Component({

  selector: 'app-eventsample4',

  templateUrl: './eventsample4.component.html',

  styleUrls: ['./eventsample4.component.css']

})

export class Eventsample4Component {

public Mobiles=[

  {Name:'OnePlus',Photo:'assets/OnePlus.jpg'},

  {Name:'Iphone',Photo:'assets/Iphone.jpg'},

  {Name:'Nokia',Photo:'assets/nokia.jpg'},

];

public Electronics=[

  {Name:'Samsung',Photo:'assets/Samsung.jpg'},

  {Name:'Sony',Photo:'assets/Sony.jpg'},

  {Name:'Aiwa',Photo:'assets/aiwa.jpg'},

];

public title:any;

public imgsrc:any;

public slidervalue:any=2;

public albumName:any;

public SlideShow()

{

  switch(this.albumName)

  {

    case 'MobileAlbum':

      this.title=this.Mobiles[this.slidervalue].Name;

      this.imgsrc=this.Mobiles[this.slidervalue].Photo;

    break;

    case 'ElectronicsAlbum':

      this.title=this.Electronics[this.slidervalue].Name;

      this.imgsrc=this.Electronics[this.slidervalue].Photo;

    break;

  }

}

}

.html Changes

<div class="container">

    <fieldset>

        <legend> Choose Photo Album</legend>

        <select [(ngModel)]="albumName" (change)="SlideShow()">

            <option value="MobileAlbum"> Mobiles</option>

            <option value="ElectronicsAlbum"> Electronics</option>

        </select>

    </fieldset>

</div>

<table width="600" border="0" cellspacing="5" cellpadding="5" align="center">

    <caption> Image Slide Show</caption>

    <tr class ="text-center">

        <td> {{title}} </td>

    </tr>

    <tr class="text-center">

    <td>

         <img [src]="imgsrc" width="400" height="250">

    </td>

    </tr>

    <tr class="text-center">

        <td>

            <input [(ngModel)]="slidervalue" type="range"

            value="0" min="0" max="2"

            (change)="SlideShow()">

        </td>

    </tr>

</table>

Next: Make changes to appmodule, and index.html as per previous examples

Output

On moving slider

Example 2:

Working with cascade dropdown

Add a new component

ng g c eventsample5

.ts File

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

@Component({

  selector: 'app-eventsample5',

  templateUrl: './eventsample5.component.html',

  styleUrls: ['./eventsample5.component.css']

})

export class Eventsample5Component {

  public categories=['Select Category','Electronics','Mobiles'];

  public electronics=['Select Product', 'Samsung TV','Sony TV','Aiwa TV'];

  public mobiles=['Select Product','Nokia','Iphone'];

  public datable=[

    {Name:'Samsung TV',Price:450,Photo:'assets/Samsung.jpg'},

    {Name:'Nokia',Price:4590,Photo:'assets/nokia.jpg'},

    {Name:'Sony TV',Price:40050,Photo:'assets/Sony.jpg'},

    {Name:'Aiwa TV',Price:750,Photo:'assets/aiwa.jpg'},

    {Name:'Iphone',Price:850,Photo:'assets/Iphone.jpg'},

  ];

  public prods:string[] | undefined;

  public mobprods:string[] | undefined;

  public lstCategories:any

  public lstProducts:any;

  public ProdName:any;

  public ProdPrice:any;

  public ProdPhoto:any;

  public qty=1;

  public GetDetails(index:number)

  {

    this.ProdName=this.datable[index].Name;

    this.ProdPhoto=this.datable[index].Photo;

    this.ProdPrice=this.datable[index].Price;

  }

  public SelectedCategoryChanged()

  {

    switch(this.lstCategories) {

      case 'Electronics':

      this.prods=this.electronics;

      break;

      case 'Mobiles':

      this.prods=this.mobiles;

      break;

      default:

        alert('Please Select Category');

        this.prods=['Select Product'];

    }

  }

  public SelectedProductChanged()

  {

    switch(this.lstProducts) {

      case 'Samsung TV':

        this.GetDetails(0);

        break;

      case 'Nokia':

        this.GetDetails(1);

        break;

      case 'Sony TV':

        this.GetDetails(2);

        break;

      case 'Aiwa TV':

        this.GetDetails(3);

        break;

      case 'Iphone':

        this.GetDetails(4);

        break;

      default:

        alert('Please Select Product');

    }

  }

}

.html File

<div class="container">

    <h2>Shopping Cart</h2>

    <table width="400" align="center">

        <tr>

            <td>

                <label class="control-label">Select Category</label>

                <select [(ngModel)]="lstCategories" (change)="SelectedCategoryChanged()"

                class="form-control">

                    <option *ngFor ="let item of categories">

                {{item}}

            </option>

            </select>

            </td>

        </tr>

        <tr>

            <td>

                <label class="control-label">Select Product</label>

                <select [(ngModel)]="lstProducts" (change)="SelectedProductChanged()"

                class="form-control">

                    <option *ngFor ="let item of prods">

                {{item}}

            </option>

            </select>

            </td>

        </tr>

        <tr>

            <td>

                <label class="control-label">Preview</label>

                <h3> {{ProdName }}</h3>

                <img [src]="ProdPhoto" width="300" height="250">

                <label class="control-label" > {{ProdPrice | currency:'INR'}} |  

                    Choose Quantity</label>

                <input [(ngModel)]="qty" [value]="qty" type="number" min="1" max="5">

                <label class="control-label">Total Amount : {{qty * ProdPrice }}</label>

            </td>

        </tr>

    </table>

</div>

Next, make changes to appmodule.ts and index.html file as per previous examples

Output

Event Binding in Angular Part

 What is Event

Event is a message sent by sender to its subscriber in order to notify the change.

Event follows a communication design pattern called observer.

Observer is a behavioural pattern which defines a communication between object and the action it have to perform.

Event uses an Event Handler that follows Delegate Mechanism(Function Pointer)

Event is associated with Browser in client side scripting and the browser event are categorized into three types

 Mouse Events

 Key Events

 Mis Events

Angular binds an event with any element by using the ()

Syntax:

<button (eventName)="function()">

Example of Event Handler  

Create a component

ng g c eventsample1

.TS File Changes

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

@Component({

  selector: 'app-eventsample1',

  templateUrl: './eventsample1.component.html',

  styleUrls: ['./eventsample1.component.css']

})

export class Eventsample1Component {

public ShowAlert()

{

  alert('Event Fire up');

}

}

ScreenShot

html changes

<button (click)="ShowAlert()">Submit </button>

<br/>

<select (change)="ShowAlert()">

    <option>Delhi</option>

    <option>Hyderabad</option>

</select>

Output:

    

Example 2:

Event Argument

Every point of browser with a set of properties like screenx, clientx, alt key, shift key, keycode,

etc

Event can pass the properties to function by using $Event as event argument.

Example on Colour Panel

Red

Green

Blue

.ts Changes

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

@Component({

  selector: 'app-eventsample2',

  templateUrl: './eventsample2.component.html',

  styleUrls: ['./eventsample2.component.css']

})

export class Eventsample2Component {

public colorName:any;

public GetColor(eventArgs:MouseEvent)

{

  if(eventArgs.clientX>1 && eventArgs.clientX<=179)

  {

    this.colorName='Red';

  }

  else if(eventArgs.clientX>184 && eventArgs.clientX<=398)

  {

    this.colorName='Green';

  }

  else if(eventArgs.clientX>404 && eventArgs.clientX<=557)

  {

    this.colorName='Blue';

  }

}

public SetColor() {

  let color={

    'color': this.colorName,

  };

  return color;

}

ScreenShot

html changes

<div class="container">

    <h2> color panel </h2>

<img (click)="GetColor($event)"  width="800" height="850" src="assets/panel.png">

<br/>

<div>

    <h2 [ngStyle]="SetColor()"> Sample Text with {{ colorName }} color</h2>

</div>

</div>

ScreenShot

Output

When clicked on green Color

Blue Color

Example 3

With KeyEvents

Create Component

ng g c eventsample3

.TS Changes

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

@Component({

  selector: 'app-eventsample3',

  templateUrl: './eventsample3.component.html',

  styleUrls: ['./eventsample3.component.css']

})

export class Eventsample3Component {

public UsersData=[

  {UserId:'John'},

  {UserId:'John12'},

  {UserId:'John1234'},

  {UserId:'John123'},

  {UserId:'david'}

];

public UserId:any;

public Pwd:any;

public regExp=/^[A-Za-z]\w{7,14}$/

public msgUserId:any;

public msgPwd:any;

public min:number=0;

public max:any=0;

public value:any=0;

public low:any=0;

public high:any=0;

public CheckUserId() {

    for(let i=0;i<this.UsersData.length;i++) {

      if(this.UsersData[i].UserId==this.UserId)

      {

      this.msgUserId='User Id already Exist';

      return;

      }

      else{

        this.msgUserId='User Id available';

      }

    }

  }

  public GetGrade(min: number,max: number,value: number,low: number,high: number)

  {

    this.min=min;

    this.max=max;

    this.value=value;

    this.low=low;

    this.high=high;

  }

  public CheckPassWord()

  {

    if(this.Pwd.match(this.regExp))

    {

      this.msgPwd='Strong Password';

      this.GetGrade(1,100,100,60,80);

    }

    else{

      this.msgPwd='Weak Password';

      this.GetGrade(1,100,100,40,80);

    }

  }

}

.htmlChanges

<div class="container">

    <h3> Register</h3>

    <dl>

        <dt>User Id</dt>

        <dd><input type="text"[(ngModel)]="UserId" (keyup)="CheckUserId()">

        <span>{{msgUserId}}</span></dd>

        <dt>Password</dt>

        <dd><input type="password"[(ngModel)]="Pwd" (keyup)="CheckPassWord()">

        <span>

            {{msgPwd}}

        </span>

        <meter min="{{min}}" max="{{max}}" value="{{value}}" low="{{low}}"

        high="{{high}}"></meter> </dd>

    </dl>

</div>

ScreenShot

Output

We can Also Add KeyCodes to check caps status by using keycode

In the above same code.

Add this method and declare the variable msg at the top(public msg:any)

public CheckCaps(event: KeyboardEvent)

  {

    if (event.getModifierState && event.getModifierState('CapsLock')) {

      this.msg='Caps is on';

     } else {

      this.msg='';

     }

  }

ScreenShot