Question 1

What is AngularJS and how does it differ from Angular?

Accepted Answer

AngularJS is a JavaScript MVC framework for building dynamic web apps. Angular (2+) is a complete rewrite using TypeScript with components instead of controllers, better performance, and mobile support.

Question 2

What is $scope in AngularJS?

Accepted Answer

$scope is an object that binds controllers to views, enabling two-way data binding. It's the glue between your JavaScript code and HTML templates, automatically syncing model changes to the view.

Question 3

What is the digest cycle in AngularJS?

Accepted Answer

The digest cycle is AngularJS's change detection mechanism. It loops through all watchers, checks for changes, and updates the DOM. It runs automatically after user events, HTTP responses, and $timeout calls.

Question 4

What is two-way data binding in AngularJS?

Accepted Answer

Two-way data binding automatically synchronizes data between model ($scope) and view (HTML). Changes in the input field update the model, and model changes update the view, using ng-model directive.

Question 5

What is the difference between ng-show/ng-hide and ng-if?

Accepted Answer

ng-show/ng-hide toggle CSS display property while keeping elements in DOM. ng-if actually adds/removes elements from DOM, destroying scope and watchers. Use ng-if for better performance with rarely shown content.

Question 6

What is the difference between service, factory, and provider?

Accepted Answer

Service uses 'new' to create instance, factory returns any value from a function, provider is configurable during config phase. Factory is most flexible, provider is needed for app-wide configuration.

Question 7

How does dependency injection work in AngularJS?

Accepted Answer

AngularJS automatically provides dependencies by name. Declare dependencies as function parameters, and the injector creates/provides them. Use $inject annotation for minification safety.

Question 8

What are directives in AngularJS?

Accepted Answer

Directives extend HTML with custom attributes, elements, or classes. Built-in directives include ng-repeat, ng-model, ng-click. Custom directives encapsulate reusable DOM manipulation and behavior.

Question 9

What is ng-repeat and how does it work?

Accepted Answer

ng-repeat iterates over collections to create DOM elements. It creates a child scope for each item with $index, $first, $last variables. Use track by for better performance with large lists.

Question 10

What is the controller as syntax and why is it preferred?

Accepted Answer

Controller as syntax binds controller to view as a named object (e.g., 'vm'). It avoids $scope confusion, prevents prototype inheritance issues, and makes clear which controller owns each property.

Question 11

What is $apply and when should you use it?

Accepted Answer

$apply triggers the digest cycle manually. Use it when updating scope from outside AngularJS context (setTimeout, jQuery events, third-party callbacks) to sync changes with the view.

Question 12

What is $watch and what are its performance implications?

Accepted Answer

$watch registers a listener for scope changes. Each watcher runs during every digest cycle, so too many watchers slow performance. Use one-time binding (::) or track by to reduce watchers.

Question 13

How does form validation work in AngularJS?

Accepted Answer

AngularJS provides built-in validation with ng-required, ng-minlength, ng-pattern directives. Forms expose $valid, $invalid, $pristine, $dirty states. CSS classes like ng-invalid enable visual feedback.

Question 14

What is the difference between ng-route and ui-router?

Accepted Answer

ng-route is AngularJS's basic router supporting single views. ui-router supports nested views, multiple named views, and state-based routing. ui-router is more powerful for complex applications.

Question 15

What is ngUpgrade and how does it help with migration?

Accepted Answer

ngUpgrade allows running AngularJS and Angular side by side in the same app. It enables incremental migration by upgrading AngularJS components to Angular or downgrading Angular components for use in AngularJS.

AngularJS Fundamentals(6 questions)

What is AngularJS and how does it differ from Angular (2+)?

What is the MVC/MVW architecture in AngularJS?

What are modules in AngularJS and how do you create one?

What is $scope in AngularJS?

What is $rootScope and how does it differ from $scope?

What is two-way data binding in AngularJS?

Controllers(5 questions)

What is a controller in AngularJS?

How do you define a controller in AngularJS?

What is the "controller as" syntax and why is it preferred?

How do you share data between controllers?

What are the best practices for writing controllers?

Directives(7 questions)

What are directives in AngularJS?

What is the difference between ng-show/ng-hide and ng-if?

What is ng-repeat and how does it work?

How do you create a custom directive?

What is the difference between restrict options (E, A, C, M)?

What is the link function in a directive?

What is the compile function and how does it differ from link?

Services and Dependency Injection(5 questions)

What are services in AngularJS?

What is the difference between service, factory, and provider?

How does dependency injection work in AngularJS?

What is $inject and why is it used for minification safety?

What are built-in services ($http, $timeout, $interval, $q)?

Filters(4 questions)

What are filters in AngularJS?

How do you use built-in filters (currency, date, filter, orderBy)?

How do you create a custom filter?

What is the performance impact of filters?

Routing(4 questions)

What is ng-route and how do you configure routing?

What is the difference between ng-route and ui-router?

How do you pass parameters to routes?

What are resolve functions in routing?

Forms and Validation(4 questions)

How does form validation work in AngularJS?

What are ng-model and ng-bind?

What form validation directives are available (ng-required, ng-minlength, ng-pattern)?

How do you handle form submission in AngularJS?

Digest Cycle and Performance(5 questions)

What is the digest cycle in AngularJS?

What is $apply and when should you use it?

What is $watch and what are its performance implications?

How do you optimize AngularJS application performance?

What is one-time binding (::) and when should you use it?

Testing and Migration(4 questions)

How do you unit test AngularJS applications?

What is ngMock and how is it used in testing?

What are the strategies for migrating from AngularJS to Angular?

What is ngUpgrade and how does it help with migration?