Download Angularjs and more Slides Programming Languages in PDF only on Docsity!
AngularJS Notes
By www.questpond.com
www.stepbystepschools.net
- AngularJS Notes Contents
- Introduction.................................................................................................................................
- What is AngularJS ?....................................................................................................................
- Explain Directives in Angular?...................................................................................................
- What are controllers and need of ng-controller and ng-model in Angular?
- What are expressions in Angular?
- How can we initialize Angular application data?
- Explain $scope in Angular?
- What is “$rootScope” and how is it related with “$scope”?
- Do I need Jquery for Angular?..................................................................................................
- How is the data binding in Angular?
- How do we make HTTP get and post calls in Angular?...........................................................
- How do we pass data using HTTP POST in Angular?
- What is dependency injection and how does it work in Angular?............................................
- How does DI benefit in Angular?
- What are services in Angular?
- Are Service object instances global or local?
- What is a Factory in Angular?
- What is the difference between Factory and Service?
- How are validations implemented in Angular?
- How to check error validation for a specific field?...................................................................
- What does SPA (Single page application) mean?.....................................................................
- How can we implement SPA with Angular?
- How to implement routing in Angular?
Introduction
These notes will help you to kick start learning AngularJS within 5 minutes. We have kept the
format of the notes in Q and A format so that you can learn easily and quickly.
We highly encourage you to see our Learn MVC with Angular in 2 days i.e. (16 hours) video
series before reading this document https://www.youtube.com/watch?v=Lp7nSImO5vk
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.
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() {
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 Directives in Angular?
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.
Some of the most commonly used directives are ng-app,ng-controller and ng-repeat.
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.
What are expressions in Angular?
Angular expressions are 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.
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.
The value of Customer code is {{CustomerCode}}
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.
The value of pi is {{pi}}
Explain $scope in Angular?
“$scope” is an object instance of a controller. “$scope” object instance get’s created when “ng-controller”
directive is encountered.
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 $scope object.
What is “$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
from the expression and attaches this variable to the “$rootScope” object created in Step 1.
Step 3:- Parser then finds the first “DIV” tag with “ng-controller” directive which is pointing to
“Function1” controller. Looking at the “ng-controller” directive it creates a “$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.
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.
Do I need Jquery for Angular?
No , you do not need Jquery for Angular. It’s independent of Jquery.
How is the data binding in Angular?
Its two way binding. So whenever you make changes in one entity the other entity also gets updated.
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.
$http({ method: "GET", url: "http://localhost:8438/SomeMethod" }).success(function (data, status, headers, config) { // Here goes code after success }
How do we pass data using HTTP POST in Angular?
You need to pass data using the “data” keyword in the “$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”; $http({ method: "POST", data: myData, url: "http://www.xyz.com"}) .success(function (data, status, headers, config) { // Here goes code after success }
What is dependency injection and how does it work in Angular?
Dependency injection is a process where we inject the dependent objects rather than consumer
creating the objects. DI is everywhere in Angular or we can go one step ahead and say Angular
cannot work without DI.
For example in the below code “$scope” and “$http” objects are created and injected by the
angular framework. The consumer i.e. “CustomerController” does not create these objects
himself rather Angular injects these objects.
function Customer($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 “$http” object and run your customer class offline without errors.The fake
object is injected using DI.
What are services in Angular?
Service helps to implement dependency injection. For instance let’s say we have the below
“Customer” class who needs “Logger” object. Now “Logger” object can be of “FileLogger” type
or “EventLogger” type.
function Customer($scope,$http, Logger) {
$scope.Logger = Logger; }
So you can use the “service” method of the application and tie up the “EventLogger” object with
the “Logger” input parameter of the “Customer” class.
var app = angular.module("myApp", []); // creating a APP app.controller("Customer", Customer); // Registering the VM app.service("Logger", EventLogger); // Injects a global Event logger object
So when the controller object is created the “EventLogger” object is injected automatically in the
controller class.
Are Service object instances global or local?
Angular Services create and inject global instances. For example below is a simple “HitCounter”
class which has a “Hit” function and this function increments the variable count internally every
time you call hit the button.
function HitCounter() { var i = 0; this.Hit = function () { i++; alert(i); }; }
This “HitCounter” class object is injected in “MyClass” class as shown in the below code.
function MyClass($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.
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.
function CreateAddress() { var add = new Address(); return add; } function CreatePhone() { 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.
$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.
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”.
