Angular.js interview questions

Angular.js interview questions

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  ANGULAR.JS INTERVIEW QUESTIONS 1)What is Angular.js? AngularJS is a javascript framework used for creating singleweb page applications. Itallows you to useHTML as your template language and enables you to extend HTML’s syntaxto express your application’s components clearly 2) Explain what are the key features of Angular.js ? The key features of angular.js are  Scope  Controller  Model  View  Services  Data Binding  Directives  Filters  Testable 3) Explain what is scope in Angular.js ?
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  Scope refers tothe application model, it acts like glue between application controller and the view. Scopes are arranged in hierarchicalstructureand impersonate the DOM( Document ObjectModel) structureof the application. It can watch expressions and propagate events. 4) Explain what is services inAngular.js ? In angular.js services arethe singleton objects or functions that are used for carrying out specific tasks. Itholds some business logic and these function can be called as controllers, directive, filters and so on. 5) Explain what is Angular Expression? Explain what is key difference between angular expressions andJavaScript expressions? Like JavaScript, Angular expressions arecode snippets that are usually placed in binding such as {{ expression }} The key difference between the JavaScriptexpressions and Angular expressions  Context :In Angular, the expressions areevaluated against a scopeobject, while the Javascriptexpressions areevaluated againstthe global window  Forgiving: In Angular expression evaluation is forgiving to null and undefined, while in Javascriptundefined properties generates TypeError or ReferenceError  No Control Flow Statements: Loops, conditionals or exceptions cannot be used in an angular expression  Filters: To formatdata before displaying it you can usefilters 6) Withoptions on page load how you can initialize aselect box ? You can initialize a select box with options on page load by using ng-init directive  <div ng-controller = “ apps/dashboard/account” ng-switch
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   On =“! ! accounts” ng-init = “ loadData ( ) ”> 7) Explain what are directives ? Mention some of the most commonly used directivesinAngular.js application ? A directive is something that introduces new syntax, they are like markers on DOMelement which attaches a special behavior to it. In any Angular.js 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. 8) Mention what are the advantages of using Angular.js ? Angular.js has severaladvantages in web development.  Angular.js supports MVS pattern  Can do two ways data binding using Angular.js  Ithas per-defined formvalidations  Itsupports both client server communication  Itsupports animations 9) 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 bookmarkableURL in Angular.js is called a route A value in Angular JS is a simple object. Itcan 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
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  10) Explain whatis data binding in Angular.js ? Automatic synchronization of data between the model and view components is referred as data binding in Angular.js. Thereare two ways for data binding 1. Data mining in classical template systems 2. Data binding in angular templates 11) What makes angular.js better ?  Registering Callbacks: Thereis 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 DOMalthough it can be done if it is required  Transfer data to and from the UI: 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 dueto flow of marshalling data  No initilization code:With angular.js you can bootstrap your app easily using services, which auto-injected into your application in Guice like dependency injection style 12) Explain what is string interpolation inangular.js ? In angular.js thecompiler during the compilation process matches text and attributes using interpolate serviceto see if they contains embedded expressions. As partof normaldigest cycle these expressions areupdated and registered as watches. 13) Mention the steps for the compilation process of HTML happens?
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  Compilation of HTMLprocess occurs in following ways  Using the standard browser API,firsttheHTML is parsed into DOM  By using the call to the $compile () method, compilation of the DOMis performed. The method traverses the DOMand matches the directives.  Link the template with scope by calling the linking function returned fromthe previous step 14) Explain what is directive andMention what are the different types of Directive? During compilation process when specific HTML constructs are encountered a behaviour or function is triggered, this function is referred as directive. Itis executed when the compiler encounters it in the DOM. Different types of directives are  Element directives  Attribute directives  CSS class directives  Comment directives 15) Explain what is linking function and type of linking function? Link combines the directives with a scope and produce a live view. For registering DOMlisteners as well as updating the DOM, link function is responsible. After the template is cloned it is executed.  Pre-linking function: Pre-linking function is executed before the child elements are linked. Itis not considered as the safe way for DOMtransformation.  Postlinking function: Postlinking function is executed after the child elements are linked. Itis safeto do DOMtransformation by post-linking function 16) Explain what is injector?
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  An injector isa service locator. It is used to retrieve object instances as defined by provider, instantiate types, invokemethods and load modules. There is a single injector per Angular application, it helps to look up an object instance by its name. 17) Explain what is the difference betweenlink andcompile in angular.js?  Compile function: Itis used for template DOMManipulation and collect all of the directives.  Link function: Itis used for registering DOMlisteners as well as instance DOM manipulation. Itis executed once the template has been cloned. 18) Explain what is factory method in angular.js? For creating the directive, factory method is used. Itis invoked only once, when compiler matches the directive for the first time. By using $injector.invokethe factory method is invoked. 19) Mention what are the styling formthat ngModel adds toCSS classes ? ngModel adds these CSS classes to allow styling of formas well as control  ng- valid  ng- invalid  ng-pristine  ng-dirty 20) Mention what are the characteristics of “Scope”?  To observer model mutations scopes provideAPIs ($watch)  To propagate any model changes through the systeminto the view from outside of the Angular realm
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   A scopeinheritsproperties from its parentscope, while providing access to shared model properties, scopes can be nested to isolate application components  Scope provides context againstwhich expressions areevaluated 21) 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 softwaredesign 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 thatobject 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 whereit is required 22) Mention what are the advantages of using Angular.js framework ? Advantages of using Angular.js as framework are  Supports two way data-binding  Supports MVCpattern  Supportstatic template and angular template  Can add customdirective  Supports RESTfull services  Supports form validations  Supportboth client and server communication  Supportdependency injection  Applying Animations
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   Event Handlers 23)Explain the concept of scope hierarchy? How many scope can an application have? Each angular application consistof one rootscope but may have severalchild scopes. As child controllers and somedirectives create new child scopes, application can have multiple scopes. When new scopes are formed or created they are added as a children of their parentscope. Similar to DOM, they also creates a hierarchical structure. 24) Explain what is the difference between angular.js andbackbone.js? Angular.js combines the functionalities of mostof the 3rd party libraries, it supports individualfunctionalities required to develop HTML5 Apps. While Backbone.js do their jobs individually. 25) Who created Angular JS ? Intially it was developed by Misko Hevery and Adam Abrons. Currently it is being developed by Google. 26) What is ng-cloak ? ngCloak directive stop such type flicking issuein AngularJs. ngCloak work when application bootstrapping . Itwill add ngCloak class on run-time till application bootstrapped and ngCloak removethis class when application bootstrapped successfully. Means ngCloak directiveadd ngCloak class on selected element and remove ngCloak class when page loaded . 27) What is $rootScope ? $rootScopeis a parentscope of all $scopeand can be shared to all $scope.One application can have only one $rootScope. $scopeis a JavaScriptobject
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  associated to controllerbut $rootScopeis not. 28) What is use of ng-if ? ng-if directive removeDOMelement if expression return false. And if expression return true then it recreates a DOMtree again. 29) What is use of ng-show ? ng-show useto show and hide elements fromDOMbut withoutmanipulation in DOM. The main difference between ng-if and ng-show is ng-show add "class='ng- hide'" attribute into element if expression return false and remove "class="ng- hide" attribute fromelement when expression return true . More AngularJs Articles WHAT IS $ROOTSCOPE IN ANGULARJS UNDERSTANDING NG-IF,NG-SWITCH,NG-SHOW AND NG-REPEAT DIRECTIVES WHAT IS NG-CLOAK DIRECTIVE IN ANGULARJS? YPESCRIPT + ANGULAR 2 - ANGULARJS 2 WILL BE DEVELOPED WITH TYPESCRIPT DIFFERENT WAY TO WORK WITH NGCLASS WHAT IS SCOPE AND SCOPE INHERITANCE INJECTING SERVICE TO DIRECTIVES IN ANGULARJS HOW TO SHOW SPARKLINES IN ANGULARJS HOW TO SET TITLE DYNAMICALLY IN ANGULARJS HOW TO CALL REST API IN ANGULARJS HOW ROUTE WORK ON ANUGLARJS