Explain $q service, deferred and promises?

Promises are POST PROCESSING LOGICS which you want to execute after some operation / action is completed. While deferred helps to control how and when those promise logics will execute.
We can think about promises as “WHAT” we want to fire after an operation is completed while deferred controls “WHEN” and “HOW” those promises will execute.
For example after an operation is complete you want to a send a mail, log in to log file and so on. So these operations you will define using promise. And these promise logics will be controlled by deferred.

We are thankful to www.stepbystepschools.net for the above image. So once some action completes deferred gives a signal “Resolve”, “Reject” or “Notify” and depending on what kind of signal is sent the appropriate promise logic chain fires.
“$q” is the angular service which provides promises and deferred functionality.
Using promises, deferred and “q” service is a 4 step process:-

• Step 1:- Get the “q” service injected from Angular.
• Step 2 :- Get deferred object from “q” service object.
• Step 3 :- Get Promise object from deferred object.
• Step 4 :- Add logics to the promise object.

Below is the angular code for the above 4 steps.

// Step 1 :- Get the "q" service
    function SomeClass($scope,$q) {

// Step 2 :- get deferred  from "q" service
        var defer = $q.defer();
// step 3:-  get promise  from defer
        var promise = defer.promise;
// step 4 :- add success and failure logics to promise object
promise.then(function () {
            alert("Logic1 success");
        }, function () {
            alert("Logic 1 failure");
        });

promise.then(function () {
            alert("Logic 2 success");
        }, function () {
            alert("Logic 2 failure");
        });

    }

So now depending on situations you can signal your promise logics via deferred to either fire the success events or the failure events.

// This will execute success logics of promise 
defer.resolve();

// This will execute failure logics of promise
defer.reject();

Can I set an Angular directive template to a HTML web page?

Yes, you can set template to page directly by using “templateUrl” property of the directive as shown in the code snippet below.

directive.templateUrl = "/templates/footer.html";

What if I want custom directives to be applied on element as well as attributes ?

directive.restrict = 'EA';

What are the different custom directive types in AngularJS?

There are different flavors of Angular directives depending till what level you want to restrict your custom directive.
In other words do you want your custom directive to be applied only on HTML element or only on an attribute or just to CSS etc.
So in all there are four different kinds of custom directives:-

• Element directives (E)
• Attribute directives (A)
• CSS class directives (C)
• Comment directives (M)

Below is a simple custom directive implementation at the element level.

myapp.directive('userinfo', function()
{
    var directive = {};
    directive.restrict = 'E';
    directive.template = "User : {{user.firstName}} {{user.lastName}}";
    return directie;
});

The “restrict” property is set to “E” which means that this directive can only be used at element level as shown in the code snippet below.

<userinfo></userinfo>

If you try to use it at an attribute level as shown in the below code it will not work.

<div userinfo></div>

So “E” for element, “A” for attribute, “C” for CSS and “M” for comments.

What kind of naming conventions is used for custom directives?

For angular custom directive the best practice is to follow camel casing and that also with atleast two letter’s. In camel case naming convention we start with a small letter, followed by a capital letter for every word.
Some example of camel cases are “loopCounter” , “isValid” and so on.
So when you register a custom directive it should be with camel case format as shown in the below code “companyCopyRight”.

app.directive('companyCopyRight', function ()
{
return
{
        template: '@CopyRight questpond.com '
 };
});

Later when this directive is consumed inside HTML before each capital letter of camel case we need to insert a “-“ as specified in the below code.

<div company-copy-right></div>

If you are making a one letter prefix like “copyright” it’s very much possible that tomorrow if HTML team creates a tag with the same name, it will clash with your custom directive. That’s why angular team recommends camel case which inserts a “-“ in between to avoid further collision with future HTML tag’s.

How can we create a custom directive in Angular?

Till now we have looked in to predefined Angular directives like “ng-controller”,”ng-model” and so on. But what if we want to create our own custom Angular directive and attach it with HTML elements as shown in the below code.

<div id=footercompany-copy-right></div>

To create a custom directive we need to use the “directive” function to register the directive with angular application. When we call the “register” method of “directive” we need to specify the function which will provide the logic for that directive.
For example in the below code we have created a copy right directive and it returns a copy right text.
Please note “app” is an angular application object which has been explained in the previous sections.

app.directive('companyCopyRight', function ()
{
return
{
        template: '@CopyRight questpond.com '
 };
});

The above custom directive can be later used in elements as shown in below code.

<div ng-controller="CustomerViewModel">
<div company-copy-right></div>
</div>

How to implement routing in Angular?

Implementing Angular route is a five step process: -
Step 1: - Add the “Angular-route.js” file to your view.

<script src="~/Scripts/angular-route.js"></script>

Step 2: - Inject “ngroute” functionality while creating Angular app object.

var app = angular.module("myApp", ['ngRoute']);

Step 3: - Configure the route provider.
In route provider we need to define which URL pattern will load which view. For instance in the below code we are saying “Home” loads “Yoursite/Home” view and “Search” loads “YourSite/Search” view.

app.config(['$routeProvider',
            function ($routeProvider) {;

                $routeProvider.
                        when('/Home, {
                            templateUrl: 'Yoursite/Home',
                            controller: 'HomeController'
                        }).
                        when('/Search', {
                            templateUrl: YourSite/Search',
                            controller: 'SearchController'
                        }).
                        otherwise({
                            redirectTo: '/'
                        });
            }]);

Step 4: - Define hyperlinks.
Define hyper link with the “#” structure as shown below. So now when user clicks on the below anchor hyperlinks, these actions are forwarded to route provider and router provider loads the view accordingly.

Home
Search

Step 5: - Define sections where to load the view.
Once the action comes to the router provider it needs a place holder to load views. That’s defined by using the “ng-view” tag on a HTML element. You can see in the below code we have created a “DIV” tag with a place holder. So the view will load in this section.

So if we summarize angular routing is a three step process (Below is a visual diagram for the same): -

• Step 1: - End user clicks on a hyperlink or button and generates action.
• Step 2: - This action is routed to the route provider.
• Step 3: - Router provider scans the URL and loads the view in the place holder defined by “ng-view” attribute.

How can we implement SPA with Angular?

By using Angular routes.

What does SPA (Single page application) mean?

SPA is a concept where rather loading pages from the server by doing post backs we create a single shell page or master page and load the webpages inside that master page.

How are validations implemented in Angular?

Angular leverages HTML 5 validations and new form element types to implement validation.

For instance below is a simple form which has two text boxes. We have used HTML 5 “required” validation attribute and a form element of type “email”.

<form name="frm1" id="frm1" >
Name :- <input type=text name="CustomerName" id="CustomerName" required />      Email :- <input type=email  name="Email" id="Email" />
<input type=submit value="Click here"/>
</form>

Below are some example of new form elements introduced in HTML 5 and Angular works with almost all of them :-

• Color.
• Date
• Datetime-local
• Email
• Time
• Url
• Range
• Telephone
• Number
• Search

When you run the above HTML inside a browser which understands HTML 5 , you will see your validations and form types in actions as shown in the below browser screen shot.

Angular leverages HTML 5 validation attributes and new HTML 5 form elements. Now if we want Angular to handle validation we need first stop HTML 5 to do validation. So for that the first step is to specify “novalidate” attribute on the form tag.

<form name="frm1" novalidate>
-----
</form>

So now the HTML will not fire those validations it will be routed to the Angular engine to further take actions.
In other words when end user fills data in the HTML UI , validation events are routed to Angular framework and depending on scenario Angular sets a field called as “$Valid”. So if the validations are fine it sets it to “True” or else its sets it to “False”.

So you can see in the below code we have attached the angular controller and models to the text boxes. Watch the code of the button it has “ng-disabled” attribute which is set via the “$Valid” property in a NEGATED fashion.
Negated fashion means when there is no error it should enable the button and when there are errors that means it’s false it should disable the button.

<form name="frm1" novalidate>
Name:-<input type=text ng-model="Customer.CustomerName" name="CustomerName" required />
Email :- <input type=email ng-model="Customer.Email" name="Email" />
<input type=submit value="Click here" ng-disabled="!(frm1.$valid)"/>
</form>

Note :- “Name” is needed for the validations to work.

What is the difference between Factory and Service?

“Factory” and “Service” are different ways of doing DI (Dependency injection) in angular. Please read the previous question to understand what is DI.
So when we define DI using “service” as shown in the code below. This creates a new GLOBAL instance of the “Logger” object and injects it in to the function.

app.service("Logger", Logger); // Injects a global object

When you define DI using a “factory” it does not create a instance. It just passes the method and later the consumer internally has to make calls to the factory for object instances.

app.factory("Customerfactory", CreateCustomer);

Below is a simple image which shows visually how DI process for “Service” is different than “Factory”.

	Factory	Service
Usage	When we want to create different types of objects depending on scenarios. For example depending on scenario we want to create a simple “Customer” object , or “Customer” with “Address” object or “Customer” with “Phone” object. See the previous question for more detailed understanding.	When we have utility or shared functions to be injected like Utility , Logger , Error handler etc.
Instance	No Instance created. A method pointer is passed.	Global and Shared instance is created.

Are Service object instances global or local?

Angular Services create and inject global instances. For example below is a simple “HitCounter” class which has a “Hit” function and this function increments the variable count internally every time you call hit the button.

function HitCounter()
{
       var i = 0;
        this.Hit = function ()
        {
            i++;
            alert(i);
        };
}

This “HitCounter” class object is injected in “MyClass” class as shown in the below code.

function MyClass($scope, HitCounter)
{
 $scope.HitCounter = HitCounter;
}

Below code advises the Angular framework to inject “HitCounter” class instance in the “MyClass” class. Read the last line of the below code specially which says to inject the inject the “HitCounter” instance.

var app = angular.module("myApp", []); // creating a APP
app.controller("MyClass", MyClass); // Registering the VM
app.service("HitCounter", HitCounter); // Injects the object

Now let’s say that the “Controller” “MyClass” is attached to twodiv tag’s as shown in the below figure.
So two instances of “MyClass” will be created. When the first instance of “MyClass” is created a “HitCounter” object instance is created and injected in to “MyClass” first instance.
When the second instance of “MyClass” is created the same “HitCounter” object instance is injected in to second instance of “MyClass”.
Again I repeat the same instance is injected in to the second instance, new instances are not created.

If you execute the above code you will see counter values getting incremented even if you are coming through different controller instances.

How does DI benefit in Angular?

There are two big benefits of DI: - Decoupling and Testing.
Let’s first start with Decoupling. Consider your application has a logger functionality which helps to log errors , warning etc in some central place. This central place can be a file, event viewer, database etc.

function FileLogger()
{
        this.Log = function () {
            alert("File logger");
        };
}
function EventLogger()
{
        this.Log = function () {
            alert("Event viewer logger");
        };
}

Now let’s say you have a “Customer” class who wants to use the “Logger” classes. Now which “Logger” class to use depends on configuration.

So the code of “Customer” is something as shown below. So depending on the configuration “Customer” class either creates “FileLogger” or it creates “EventLogger” object.

function Customer($scope, Logger)
{
        $scope.Logger = {};
        if (config.Loggertype = "File")
{
            $scope.Logger = new FileLogger();
        }
        else
{
            $scope.Logger = new EventLogger();
        }
}

But with DI our code becomes something as shown below. The “Customer” class says he is not worried from where the “Logger” object comes and which type of “Logger” objects are needed .He just wants to use the “Logger” object.

function Customer($scope,$http, Logger)
{
        $scope.Logger = Logger;
}

With this approach when a new “Logger” object gets added the “Customer” class does not have to worry about the new changes because the dependent objects are injected by some other system.
The second benefit of DI is testing. Let’s say you want to test the “Customer” class and you do not have internet connection. So your “$http” object method calls can throw errors. But now you can mock a fake “$http” object and run your customer class offline without errors.The fake object is injected using DI.

How do we pass data using HTTP POST in Angular ?

You need to pass data using the “data” keyword in the “$http” service API function. In the below code you can see we have created a javascript object “myData” with “CustomerName” property. This object is passed in the “$http” function using HTTP POST method.

Var myData = {};
myData.CustomerName = “Test”;
$http({ method: "POST",
 data: myData,
 url: "http://www.xyz.com"})
 .success(function (data, status, headers, config)
 {
   // Here goes code after success
 }

How do we make HTTP get and post calls in Angular?

To make HTTP calls we need to use the “$http” service of Angular. In order to use the http services you need to make provide the “$http” as a input in your function parameters as shown in the below code.

function CustomerController($scope,$http)
{
 $scope.Add = function()
 {
            $http({ method: "GET", url: "http://localhost:8438/SomeMethod"     }).success(function (data, status, headers, config)
  {
                   // Here goes code after success
  }
 }
}

“$http” service API needs atleast three things:-

• First what is the kind of call “POST” or “GET”.
• Second the resource URL on which the action should happen.
• Third we need to define the “success” function which will be executed once we get the response from the server.

$http({ method: "GET", url: "http://localhost:8438/SomeMethod"    }).success(function (data, status, headers, config)
{
// Here goes code after success
}

Explain compile and link phase?

At the heart Angular framework is a parser. A parser which parses the Angular directives and render’s HTML output.
Angular parser works in 3 steps:-
Step 1:- HTML browser parses the HTML and creates a DOM (Document Object Model).
Step 2:- Angular framework runs over this DOM looks at the Angular directives and manipulates the DOM accordingly.
Step 3:- This manipulated is then rendered as HTML in the browser.

Now the above angular parsing is not so simple as it looks to be. It occurs in two phases “Compile” and “Link”. Firs the compile phase occurs then the link phase.

In compile phase the angular parser starts parsing the DOM and whenever the parser encounters a directive it create a function. These functions are termed as template or compiled functions. In this phase we do not have access to the $scope data.
In the link phase the data i.e. ($scope) is attached to the template function and executed to get the final HTML output.

What is “$rootScope” and how is it related with “$scope”?

“$rootScope” is a parent object of all “$scope” angular objects created in a web page.

Let us understand how Angular does the same internally. Below is a simple Angular code which has multiple “DIV” tags and every tag is attached to a controller. So let us understand step by step how angular will parse this and how the “$rootScope” and “$scope” hierarchy is created.

The Browser first loads the above HTML page and creates a DOM (Document object model) and Angular runs over the DOM.Below are the steps how Angular creates the rootscope and scope objects.

• Step 1:- Angular parser first encounters the “ng-app” directive and creates a “$rootScope” object in memory.
• Step 2:- Angular parser moves ahead and finds the expression {{SomeValue}}. It creates a variable
• Step 3:- Parser then finds the first “DIV” tag with “ng-controller” directive which is pointing to “Function1” controller. Looking at the “ng-controller” directive it creates a “$scope” object instance for “Function1” controller. This object it then attaches to “$rootScope” object.
• Step 4:- Step 3 is then repeated by the parser every time it finds a “ng-controller” directive tag. Step 5 and Step 6 is the repetition of Step 3.

If you want to test the above fundamentals you can run the below sample Angular code. In the below sample code we have created controllers “Function1” and “Function2”. We have two counter variables one at the root scope level and other at the local controller level.

Hide   Copy Code

<script language="javascript">
function Function1($scope, $rootScope) 
{
        $rootScope.Counter = (($rootScope.Counter || 0) + 1);
        $scope.Counter = $rootScope.Counter;
        $scope.ControllerName = "Function1";
}
function Function2($scope, $rootScope) 
{
        $rootScope.Counter = (($rootScope.Counter || 0) + 1);
        $scope.ControllerName = "Function2";
}
    var app = angular.module("myApp", []); // creating a APP
    app.controller("Function1", Function1); // Registering the VM
    app.controller("Function2", Function2);

</script

Below is the HTML code for the same. You can we have attached “Function1” and “Function2” two times with “ng-controller” which means four instances will be created.

Hide   Copy Code

<body ng-app="myApp" id=1>
   Global value is {{Counter}}<br />
<div ng-controller="Function1">
       Child Instance of {{ControllerName}} created :- {{Counter}}
</div><br />
<div ng-controller="Function2">
       Child Instance of {{ControllerName}} created :- {{Counter}}
</div><br />
<div ng-controller="Function1">
        Child Instance of {{ControllerName}} created :- {{Counter}}
</div><br />
<div ng-controller="Function2">
        Child Instance of {{ControllerName}} created :- {{Counter}}
</div><br />
</body>

Above is the output of the code you can see the global variable of root scope has be incremented four times because four instances of $scope have been created inside “$rootScope” object.

Explain $scope in Angular?

“$scope” is an object instance of a controller. “$scope” object instance get’s created when “ng-controller” directive is encountered.
For example in the below code snippet we have two controllers “Function1” and “Function2”. In both the controllers we have a “ControllerName” variable.

function Function1($scope)
{
$scope.ControllerName = "Function1";        
}
function Function2($scope)
{
$scope.ControllerName = "Function2";
}

Now to attach the above controllers to HTML UI we need to use “ng-controller” directive. For instance you can see in the below code snippet how “ng-controller” directive attaches “function1” with “div1” tag and “function2” with “div2” tag.

<div id=&rdquo;div1&rdquo; ng-controller="Function1">
Instance of {{ControllerName}} created 
</div>
<div id=&rdquo;div2&rdquo; ng-controller="Function2">
Instance of {{ControllerName}} created 
</div>

So this is what happens internally. Once the HTML DOM is created Angular parser starts running on the DOM and following are the sequence of events:-

• The parser first finds “ng-controller” directive which is pointing to “Function1”. He creates a new instance of “$scope” object and connects to the “div1” UI.
• The parser then starts moving ahead and encounters one more “ng-controller” directive which is pointing to “Function2”. He creates a new instance of “$scope” object and connects to the “div2” UI.

Now once the instances are created, below is a graphical representation of the same. So the “DIV1” HTML UI is binded with “function1” $scope instance and the “DIV2” HTML UI is binded with “function2” $scope instance. In other words now anything changes in the $scope object the UI will be updated and any change in the UI will update the respective $scope object.

How can we initialize Angular application data?

We can use “ng-init” directive to achieve the same. You can see in the below example we have used “ng-init” directive to initialize the “pi” value.

<body ng-app="myApp" ng-init="pi=3.14">
The value of pi is {{pi}}
</body>

What are expressions in Angular?

Angular expressionsare unit of code which resolves to value. This code is written inside curly braces “{“.
Below are some examples of angular expressions:-
The below expression adds two constant values.

{{1+1}}

The below expression multiplies quantity and cost to get the total value.

The value total cost is {{ quantity * cost }}

The below expression displays a controller scoped variable.

<div ng-controller="CustomerVM">
The value of Customer code is {{CustomerCode}} 
</div>

The value of Customer code is {{CustomerCode}}

What are controllers and need of ng-controller and ng-model in Angular?

“Controllers” are simple javascript function which provides data and logic to HTML UI. As the name says controller they control how data flows from the server to HTML UI.

For example below is simple “Customer” controller which provides data via “CustomerName” and “CustomerCode” property and Add/ Update logic to save the data to database.

Note: - Do not worry too much about the $scope , we will discuss the same in the next question.

function Customer($scope)
{
        $scope.CustomerName = "Shiv";
        $scope.CustomerCode = "1001";
        $scope.Add = function () {
        }
        $scope.Update = function () {
        }
}

“ng-controller” is a directive.Controllers are attached to the HTML UI by using the “ng-controller” directive tag and the properties of the controller are attached by using “ng-model” directive. For example below is a simple HTML UI which is attached to the “Customer” controller via the “ng-controller” directive and the properties are binded using “ng-model” directive.

<div ng-controller="Customer">
<input type=text id="CustomerName"  ng-model="CustomerName"/><br />
<input type=text id="CustomerCode"  ng-model="CustomerCode"/>
</div>

What is AngularJS ?

“AngularJS is a JavaScript framework which simplifies binding JavaScript objects with HTML UI elements.”
Let us try to understand the above definition with simple sample code.
Below is a simple “Customer” function with “CustomerName” property. We have also created an object called as “Cust” which is of “Customer” class type.

function Customer() 
{
this.CustomerName = "AngularInterview";
}
var Cust = new Customer();

Now let us say the above customer object we want to bind to a HTML text box called as “TxtCustomerName”. In other words when we change something in the HTML text box the customer object should get updated and when something is changed internally in the customer object the UI should get updated.

<input type=text id="TxtCustomerName" onchange="UitoObject()"/>

So in order to achieve this communication between UI to object developers end up writing functions as shown below. “UitoObject” function takes data from UI and sets it to the object while the other function “ObjecttoUI” takes data from the object and sets it to UI.

function UitoObject() 
{
Cust.CustomerName = $("#TxtCustomerName").val();
}
function ObjecttoUi() 
{
$("#TxtCustomerName").val(Cust.CustomerName);
}

So if we analyze the above code visually it looks something as shown below. Your both functions are nothing but binding code logic which transfers data from UI to object and vice versa.

Now the same above code can be written in Angular as shown below. The javascript class is attached to a HTML parent div tag using “ng-controller” directive and the properties are binded directly to the text box using “ng-model” declarative.
So now whatever you type in the textbox updates the “Customer” object and when the “Customer” object gets updated it also updates the UI.

<div ng-controller="Customer">
<input type=text id="txtCustomerName"  ng-model="CustomerName"/>
</div>

In short if you now analyze the above code visually you end up with something as shown in the below figure.You have the VIEW which is in HTML, your MODEL objects which are javascript functions and the binding code in Angular.

Now that binding code have different vocabularies.

• Some developers called it “ViewModel” because it connects the “Model” and the “View” .
• Some call it “Presenter” because this logic is nothing but presentation logic.
• Some term it has “Controller” because it controls how the view and the model will communicate.

To avoid this vocabulary confusion Angular team has termed this code as “Whatever”. It’s that “Whatever” code which binds the UI and the Model. That’s why you will hear lot of developers saying Angular implements “MVW” architecture.

Explain what is DI (Dependency Injection ) and how an object or function can get a hold of its dependencies ?

DI or Dependency Injection is a software design pattern that deals with how code gets hold of its dependencies.  In order to retrieve elements of the application which is required to be configured when module gets loaded , the operation “config” uses dependency injection.
These are the ways that object uses to hold of its dependencies

• Typically using the new operator, dependency can be created
• By referring to a global variable, dependency can be looked up
• Dependency can be passed into where it is require

Mention what are the styling form that ngModel adds to CSS classes ?

ngModel adds these CSS classes to allow styling of form as well as control

• ng- valid
• ng- invalid
• ng-pristine
• ng-dirty

Explain what is factory method in AngularJS?

For creating the directive, factory method is used.  It is invoked only once, when compiler matches the directive for the first time.  By using $injector.invoke the factory method is invoked.

“Factory” in real world means a premise where products are manufactured. Let’s take an example of a computer manufacturing firm. Now the company produces different kinds and sizes of computers likelaptops,desktops, tablets etc.
Now the process of manufacturing the computer products are same with slight variation. To manufacture any computer we need processor, RAM and hard disk. But depending on what kind of final case packing is the final product shapes.

That’s what the use of Factory in Angular.
For example see the below code we have a “Customer”, “Phone” and “Address” class.

function Customer()
{
        this.CustomerCode = "1001";
        this.CustomerName = "Shiv";
}
function Phone()
{
        this.PhoneNumber = "";
}
function Address()
{
        this.Address1 = "";
        this.Address2 = "";
}

So now we would create different types of “Customer” object types using the combination of “Address” and “Phones” object.

• We would like to combine “Customer” with “Address” and create a “Customer” object which has “Address” collection inside it.
• Or must be we would like to create “Customer” object with “Phone” objects inside it.
• Or must be “Customer” object with both “Phone” and “Address” objects.

In other words we would like to have different permutation and combination to create different types of “Customer” objects.
So let’s start from bottom. Let’s create two factory function’s one which creates “Address” object and the other which creates “Phone” objects.

functionCreateAddress()
{
var add = new Address();
return add;
}
functionCreatePhone()
{
var phone =  new Phone();
return phone;
}

Now let’s create a main factory function which uses the above two small factory functions and gives us all the necessary permutation and combination.
In the below factory you can see we have three functions:-

• “CreateWithAddress” which creates “Customer” with “Address” objects inside it.
• “CreateWithPhone” which creates “Customer” object with “Phone” objects inside it.
• “CreateWithPhoneAddress” which creates “Customer” object with aggregated “Phone” and “Address” objects.

function CreateCustomer() {

return {
CreateWithAddress: function () {
varcust = new Customer();
cust.Address = CreateAddress();
returncust;
            },
CreateWithPhone: function () {
varcust = new Customer();
cust.Phone = {};
cust.Phone = CreatePhone();
returncust;
            }
            ,
CreateWithPhoneAddress: function () {
debugger;
varcust = new Customer();
cust.Phone = CreatePhone();
cust.Address = CreateAddress();
returncust;
            }
        }
    }

Below is a simple “CustomerController” which takes “CustomerFactory” as the input. Depending on “TypeOfCustomer” it creates with “Address” , “Phones” or both of them.

functionCustomerController($scope, Customerfactory)
    {

        $scope.Customer = {};
        $scope.Init = function(TypeofCustomer)
        {

if (TypeofCustomer == "1")
            {
                $scope.Customer = Customerfactory.CreateWithAddress();
            }
if (TypeofCustomer ==  "2")
            {
                $scope.Customer = Customerfactory.CreateWithPhone();
            }
if (TypeofCustomer == "3") {
                $scope.Customer = Customerfactory.CreateWithPhoneAddress();
            }
        }
    }

You also need to tell Angular that the “CreateCustomer” method needs to be passed in the input. For that we need to call the “Factory” method and map the “CreateCustomer” method with the input parameter “CustomerFactory” for dependency injection.

var app = angular.module("myApp", []); // creating a APP
app.controller("CustomerController", CustomerController); // Register the VM
app.factory("Customerfactory", CreateCustomer);

So if we consume the “CustomerController” in UI , depending on situation it creates different flavors of “Customer” object. You can in the below code we have three different “DIV” tags and depending on the “TypeofCustomer” we are displaying data.

Explain what is the difference between link and compile in Angular.js?

• Compile function: It is used for template DOM Manipulation and collect all of the directives.
• Link function: It is used for registering DOM listeners as well as instance DOM manipulation. It is executed once the template has been cloned.

What makes AngularJS better ?

• Registering Callbacks: There is no need to register callbacks . This makes your code simple and easy to debug.
• Control HTML DOM programmatically:  All the application that are created using Angular never have to manipulate the DOM although it can be done if it is required
• Transfer data to and from the UI: AngularJS helps to eliminate almost all of the boiler plate like validating the form, displaying validation errors, returning to an internal model and so on which occurs due to flow of marshalling data
• No initilization code: With AngularJS you can bootstrap your app easily using services, which auto-injected into your application in Guice like dependency injection style

Explain what Angular JS routes does ?

Angular js routes enable you to create different URLs for different content in your application.  Different URLs for different content enables user to bookmark URLs to specific content.  Each such bookmarkable URL in AngularJS is called a route
A value in Angular JS is a simple object.  It can be a number, string or JavaScript object.  Values are typically used as configuration injected into factories, services or controllers. A value should be belong to an AngularJS module.
Injecting a value into an AngularJS controller function is done by adding a parameter with the same name as the value

Explain what are directives ? Mention some of the most commonly used directives in AngularJS application ?

Directives are attributes decorated on the HTML elements. All directives start with the word “ng”. As the name says directive it directs Angular what to do.
For example below is a simple “ng-model” directive which tells angular that the HTML textbox “txtCustomerName” has to be binded with the “CustomerName” property.

<input type=text id="txtCustomerName"  ng-model="CustomerName"/> 

In other words a directive is something that introduces new syntax, they are like markers on DOM element which attaches a special behavior to it. In any AngularJS application, directives are the most important components.
Some of the commonly used directives are ng-model, ng-App, ng-bind, ng-repeat , ng-show etc.

Explain what is Angular Expression? Explain what is key difference between angular expressions and JavaScript expressions?

Like JavaScript,  Angular expressions are code snippets that are usually placed in binding such as {{ expression }}
The key difference between the JavaScript expressions and Angular expressions

• Context : In Angular, the expressions are evaluated against a scope object, while the Javascript expressions are evaluated against the global window
• Forgiving: In Angular expression evaluation is forgiving to null and undefined, while in Javascript undefined properties generates TypeError or ReferenceError
• No Control Flow Statements: Loops, conditionals or exceptions cannot be used in an angular expression
• Filters: To format data before displaying it you can use filters

Explain what is services in AngularJS ?

In AngularJS services are the singleton objects or functions that are used for carrying out specific tasks.  It holds some business logic and these function can be called as controllers, directive, filters and so on.

Service helps to implement dependency injection. For instance let’s say we have the below “Customer” class who needs “Logger” object. Now “Logger” object can be of “FileLogger” type or “EventLogger” type.

function Customer($scope,$http, Logger)
{
        $scope.Logger = Logger;
}

So you can use the “service” method of the application and tie up the “EventLogger” object with the “Logger” input parameter of the “Customer” class.

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var app = angular.module("myApp", []); // creating a APP
app.controller("Customer", Customer); // Registering the VM
app.service("Logger", EventLogger); // Injects a global Event logger object

So when the controller object is created the “EventLogger” object is injected automatically in the controller class.

Name the directive which is used to attach a controller to the DOM?

ng-controller

Name the angular function which used to determines if a reference is a number?

angular.isNumber()

Think you want to make 3 ajax request and you need to maintain order, When request 1 is completed you have to make request 2, when request 2 is completed you have to make request 3. What angular feature would you have to use in this situation.

Promise chaining

What is the difference between ng-view and ng-show?

ng-view: ng-view renders the template inside the associated element, whereas ng-show shows or hide the associated HTML element based on whether the expression provided to ngShow attribute evaluates to true or false.

Which directive can you use to pervent the html template being briefly displayed by the browser in its raw form?

ng-cloak

Name some of the most commonly used angular directives, with description?

ng-app:

     Declares the root element of an AngularJS application, under which directives can be used to declare bindings and define behavior.

ng-bind:

     Sets the text of a DOM element to the value of an expression. 
For example, <span ng-bind="name"></span> will display the value of ‘name’ inside the span element. Any changes to the variable ‘name’ in the application's scope are reflected instantly in the DOM.

ng-model:

    Similar to ng-bind, but establishes a two-way data binding between the view and the scope.

ng-model-options:

    Allows tuning how model updates are done.

ng-class:

    Allows class attributes to be dynamically loaded.

ng-controller:

    Specifies a JavaScript controller class that evaluates HTML expressions.

ng-repeat:

    Instantiate an element once per item from a collection.

ng-show & ng-hide:

    Conditionally show or hide an element, depending on the value of a boolean expression. Show and hide is achieved by setting the CSS display style.

ng-switch:

    Conditionally instantiate one template from a set of choices, depending on the value of a selection expression.

ng-view:

    The base directive responsible for handling routes that resolve JSON before rendering templates driven by specified controllers.

ng-if:

    Basic if statement directive which allow to show the following element if the conditions are true. When the condition is false, the element is removed from the DOM. When true, a clone of the compiled element is re-inserted

Which module helps to write unite tests by providing mock modules etc?

ng-mock

Name the angular module which is used to enable URL routing?

ng-route

What are Directives in AngularJS?

At a high level, directives are markers on a DOM element (such as an attribute, element name, comment or CSS class) that tell AngularJS's HTML compiler ($compile) to attach a specified behavior to that DOM element.

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Angular comes with a set of these directives built-in, like ngBind, ngModel, and ngClass. Much like you create controllers and services, you can create your own directives for Angular to use. When Angular bootstraps your application, the HTML compiler traverses the DOM matching directives against the DOM elements.