*ngFor in angular 2

 In angular 2 by using the *ngFor we can create the template(nothing but the elements or HTML tags ) building based on the collection count dynamically.

In simple, I can say the repetition of the template creation can be done by using the *ngFor.

Syntax:

<tagname *ngFor="let x of arrayofobject/array">

{{x.property/x}}

</tagname>

By using the ngFor we can do the repetition for both the array and the collection of the array of the

Validations In Angular JS

Angular provided us some of the directives that which will be helpful for the validations over the form while submitting. Not to forgot that, as angular is dealing from the client side it will not fulfill the requirement of validation in the case if user turn off/disable the javascript on the browser where the application is running.

Before going to implementation of the validations, lets go through with the following angular properties which are related to find the sate/behavior of the form.

   a)ng-valid : $valid property states that the validation rules are true over the element. The return type of the $valid is boolean which can be true or false.

b)ng-invalid : $invalid property states that the validation rule over the element are false. Here too the return type of the $invalid is boolean which can be true or false.

c)ng-pristine : $pristine states that fields in the form are not yet modified if the result is true, else viceversa.

d)ng-dirty : $dirty states that some of the fields in the form has been modified if the result is true or else viceversa.

e)ng-submitted : $submitted states that the form was submitted.

Angular also provided us the directives which can be identify the state( likely modified or not) of the input tags.

a)ng-valid : The $valid states that the input field with data is valid.

b)ng-invalid : The $invalid states that the input field with the data was invalid or not met the needs of the field.

c)ng-untouched : The $untouched property states that the concern input field was not touched at all.

d)ng-touched : The $touched property states that the concern input field was disturbed by user inputs.

e)ng-pristine : same as for the form, this states that the field was not yet modified.

f)ng-dirty : similar to the use in form level, here too states that the input field was modified.

In this article lets accomplish the validations based on some of the regular usage of requirements as follows :

a)      Disable submit button until user enter the value in textbox :

<form name="myForm">            

Username:<input type="text" name="user" ng-model="usernm" required> <br /><br />

<button type="submit" ng-disabled="myForm.user.$invalid">Submit</button>          

</form>

Result :

In the above HTML lines if we observe, I had used the ng-disabled directive which is used to disable the tag/element based on the expression provided to it. I had given the expression as the “myform.user.$invalid”, Here “myForm” is name of form. “user” is the name of the input. Make sure to provide the required attribute which belongs to HTML5.

 b)Display message if user disturbs the input text and make empty even though it’s mandatory:

<form name="myForm" >                   

            Username:<input type="text" name="user" ng-model="usernm" required>

                <span style="color: red" ng-show="myForm.user.$dirty">

                <span ng-show="myForm.user.$error.required">Username is required.</span>

                </span><br /><br />  

         <button type="submit" ng-disabled="myForm.user.$invalid">Submit</button>

    </form>

Result :

In the above markup snippet, It shows the span by usinng the ng-show expression. Here the expression “myform.user.$dirty” becomes true if the user disturbs(means like writing text or cleaning the existing text in field) the input field.

In the second span too I had used the ng-show with expression as like “myform.user.$errer.required”, it behaves based on the required attribute of the input tag.

   C)Email Validation :

<form name="myForm" >                   

    Email : <input type="email" id="txtmailid" ng-model="useremail" name="txtmailnm" />

    <span ng-show="myForm.txtmailnm.$touched && myForm.txtmailnm.$error.email">Please enter valid email id.</span><br /><br />

    <button type="submit" ng-disabled="myForm.user.$invalid">Submit</button>   

 </form>

Result :

The error message was binded in the span tag which will be shown based on the the expression provided to it to the attribute ng-show. The condition becomes true when the $touched sets to true(becomes true when user focus the tetbox ) and email input which give to the textbox of type email.

D)Dropdownlist validation :

<form name="myForm" >                   

    <select id="dept" name="depts" ng-model="seldept" required>

        <option value="">--select--</option>

        <option value="1">Developer</option>

        <option value="2">Architect</option>

        <option value="3">Tester</option>

        <option value="4">Desigener</option>       

    </select>

         <button type="submit" ng-disabled="myForm.depts.$invalid">Submit</button>   

 </form>

 Result :

Here too, my button tag will be in disabled mode until it validates the condition “myForm.depts.$invalid” with false. Here, ng-model and required attributes are mandatory to be set the validation, Where ng-model is the angular attribute and the required is the feature of HTML5.

    E)Button disabling if radiobutton not selected :

<form name="myForm" >                   

    Gender:

     <input type="radio" name="gender" ng-model="gen" value="male" required />Male

     <input type="radio" name="gender" ng-model="gen" value="female" required/>Female

     <br />

    <button type="submit" ng-disabled="myForm.gender.$invalid">Submit</button>   

 </form>

Result :

As like above cases here also, we are disabling the button untill the user selects the radiobutton by providing the exression as “myForm.gender.$invalid” . we have to make sure of providing the ng-model attribute for radio type tags.

Generating error message on button click :

This scenario is just like verifying weather our form is valid or not on clicking the submit button.So, provide a name attribute to our form as like below example and check the conditions based on our need. 

<form name="form" ng-app novalidate>

  <div class="form-group">

    <input name="first_name"

          type="text"         

          ng-model="firstnamemodel"          

          required />

  </div>

  <div ng-show="submitted && form.$invalid">

  <div ng-show="form.first_name.$error.required">

    First Name is Required

  </div>

</div>

  <button

    type="submit"   

    ng-click="submitted=true">

      Submit

  </button>

</form>

Result :

In angular we can create our own custom directives which can be used as mark up tag. So, By using the custom directives we can create a tag/attribute of input type which behaves to accept only numbers or alphabets whatever according to our requirement. In my next article I'll discuss about some regularly using custom directives.

Property Binding, Interpolation and Click event handler

In this page, lets go with the things like making/using the button click event and retrieving the data from the class.
a)Property binding :
Property binding is nothing but attaching the property value(from our ts class) to the attribute of the HTML tag. Every HTML tag will be containing the attributes. For example if we take input tag like textbox, then we can have attributes like id,name..e.t.c.
How to define the property binding ?
To bind and get the property value of a class to the attribute, firstly we need to decorate the attribute with in the open and close square brackets (  [attribute] = 'propertyname' ).

Example :

 @Component({  
  selector: 'app-root',  
  template : `<button [disabled]='btnDisabled' > Disabled </button>  
        <button [disabled]='!btnDisabled'>! Disabled </button> `   
 })  
 export class AppComponent {   
  btnDisabled : boolean = true;  
 }  

Explanation :

1)In the above example, I had taken a class “ApComponent” and added a property named isDisabled.
2)within the template of the decorater I had taken 2 HTML button tags.
3)For the both button attributes, I had attached the btnDisabled property by decorating with the open and close brackets.

Result :

b)Interpolation :

Interpolation also provides us a way for binding the property values, to make interpolation we need to enclose the property value within the double open and close curly braces ( {{ propertyname }} ).

To know about interpolation, Please have a look on my page :

Interpolation in angular 2.0

Then what makes the differences between property binding and interpolation ?

Let us try to apply interpolation for the above example :

 import { Component } from '@angular/core';  
 @Component({  
  selector: 'app-root',  
  template : `with property binding : <br/>  
        <button [disabled]='btnDisabled' > Disabled </button>         
        <button [disabled]='!btnDisabled'>! Disabled </button><br/><br/>  
        With Interpolation : <br/>      
        <button disabled={{btnDisabled}} > Disabled </button>         
        <button disabled={{!btnDisabled}}>! Disabled </button>     
        `   
 })  
 export class AppComponent {   
  btnDisabled : boolean = true;  
 }  

Result :

Explanation :
In the above example, to make differences between the interpolation and the property binding I had used both(interpolation & property binding) in the template. For the first two button tags I had used the property binding and for the next two button tags I had used the interpolation.

If you observe the result, The differences can be clearly identified. The interpolation used buttons both are in disabled mode.

Even though I had provided the not disabled {{ ! btnDisabled }} inside the interpolation, It is behaving in disabled mode itself.

Confused about Which one to prefer  ? 

If your property value is plain string value then go for interpolation {{ plaintext/string  }}.  

If your property value is other than string format, then better to choose the property binding.

Binding Click handler :

Here lets know about creation and using the click event over a button control.

In angular 2, to handle the click event, we need to attach the handler by making the attribute “click” within the open and close parenthesis  ( (click) ) And then we need to attach the function name as the value to the attribute ( (clcik)=’functionname()’ ) . The function name needs to be declared within the class of the component.

Example :

 import { Component } from '@angular/core';  
 @Component({  
  selector: 'app-root',  
  template: `count : <span>{{count}}</span><br/>  
        <button id='btn' (click)='Increment()'>Count + 1</button>`  
 })  
 export class AppComponent {  
  title = 'app';  
  //count :any = 0; //property can be of any type allowed  
  //count = 0; //allowed  
  count : number=0;  //number type allowed  
  Increment() {  
   this.count=this.count+1;  
  }  
 }  

Explanation :
In the above  example, within the template I had used the button tag with click handler by assigning the function named “Increment()”.
Within the class “AppComponent” I had taken the property named count of type number.
The function “Increment()” I had declared within the “AppComponent” Class, will increment the property “count” value whenever we click on the button.

Result :

Thank you.

A basic "Search Me" game in javascript

Search me is a game based on keywords like search,time and puzzle. This is a simple game where the user will face a 10 letter word and From that word, the user needs to search letter by letter in the given shuffled letters in matrix format with the given time. The user will earn 10 plus points for finding out the each letter.
To accomplish this, I had used only javascript code.
Algorithm I followed with text : 
1) Initially I thought about the 10 letter word displaying to user which he needs to find out and also making the first letter to be with highlighted color(whcih the usrer needs to find). For this I had taken

Interpolation In Angular 2

In general, Interpolation means injecting something within a process which is happening.
If we compare to our work: Here, we are injecting/transferring  the data from the typescript(component.ts) to the view(means our HTML file) like our template or templateurl. To define the interpolation we have to use the double curly braces{{}}. Within the curly braces we need to provide the properties that which we had declared or can be initialized as like {{propertyname}}. Internally, our angular translates the interpolation into property and fetches the related property value from the class and

First Component Creation in angular 2

In angular 2, a component plays a key role while building the UI block and its business logic and for more features. In this article lets go with creation of our own component and it's execution.

Note : By the below three points we’ll get the structured project of our angular application which I had discussed in detail in the followed link(Creating First angular 2 aplication). Here just as to rewind the things I’m speaking with the following 2 points.

1)Initially, let us create our application folder(I created folderr with nameDemoFive).

Component and Execution mapping

Unlike to angular js 1.x which is module based, Angular2.0 was component based framework. So, in this article let’s dig over the concept “Component”.

What is component ?
In simple terms, I can say that a component is nothing but the place we provide our business rules(inside a class), user interface(likely Presentation layer) information and related styles information as a group together.In the comparison words with angular js 1.x version the components are like directives.
In angular 2, after having our application structure by using “ng new appname” our angular cli will