Difficult AngularJS Interview Preparation Guide

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Each angular application consist of one root scope but may have several child scopes. As child controllers and some directives create new child scopes, application can have multiple scopes. When new scopes are formed or created they are added as a children of their parent scope. Similar to DOM, they also creates a hierarchical structure.

Angular.js combines the functionalities of most of the 3rd party libraries, it supports individual functionalities required to develop HTML5 Apps. While Backbone.js do their jobs individually.

Advantages of using Angular.js as framework are:

► Supports two way data-binding
► Supports MVC pattern
► Support static template and angular template
► Can add custom directive
► Supports REST full services
► Supports form validations
► Support both client and server communication
► Support dependency injection
► Applying Animations
► Event Handlers

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 required.

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.

► To observer model mutations scopes provide APIs ($watch).
► To propagate any model changes through the system into the view from outside of the Angular realm.
► A scope inherits properties from its parent scope, while providing access to shared model properties, scopes can be nested to isolate application components.
► Scope provides context against which expressions are evaluated.

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

► ng- valid
► ng- invalid
► ng-pristine
► ng-dirty

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.

It is used for registering DOM listeners as well as instance DOM manipulation. It is executed once the template has been cloned.

It is used for template DOM Manipulation and collect all of the directives.

Post linking function is executed after the child elements are linked. It is safe to do DOM transformation by post-linking function.

Pre-linking function is executed before the child elements are linked. It is not considered as the safe way for DOM transformation.

Link combines the directives with a scope and produce a live view. For registering DOM listeners as well as updating the DOM, link function is responsible. After the template is cloned it is executed.

Compilation of HTML process occurs in following ways:

► Using the standard browser API, first the HTML is parsed into DOM
► By using the call to the $compile () method, compilation of the DOM is performed. The method traverses the DOM and matches the directives.
► Link the template with scope by calling the linking function returned from the previous step

In angular.js the compiler during the compilation process matches text and attributes using interpolate service to see if they contains embedded expressions. As part of normal digest cycle these expressions are updated and registered as watches.

With angular.js you can bootstrap your app easily using services, which auto-injected into your application in Guice like dependency injection style.

Angular.js 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.

All the application that are created using Angular never have to manipulate the DOM although it can be done if it is required.

There is no need to register callbacks . This makes your code simple and easy to debug.

Automatic synchronization of data between the model and view components is referred as data binding in Angular.js.
There are two ways for data binding:

► Data mining in classical template systems
► Data binding in angular templates

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 Angular.js 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 Angular.js module.
Injecting a value into an Angular.js controller function is done by adding a parameter with the same name as the value.

You can initialize a select box with options on page load by using ng-init directive

► <div ng-controller = " apps/dashboard/account " ng-switch
► On = "! ! accounts" ng-init = " loadData ( ) ">

Loops, conditionals or exceptions cannot be used in an angular expression.

In Angular expression evaluation is forgiving to null and undefined, while in Javascript undefined properties generates TypeError or ReferenceError.

Angular.js has several advantages in web development:

► Angular.js supports MVS pattern
► Can do two ways data binding using Angular.js
► It has per-defined form validations
► It supports both client server communication
► It supports animations