AngularJS Interview Questions with Answers for Developers

The purpose of this question is to assess the candidate’s understanding of the AngularJS framework and its core functionalities.

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AngularJS is a structural framework for dynamic web applications. It allows HTML to be used as the template language and extends HTML's syntax to express application components clearly and succinctly. AngularJS features MVC architecture, two-way data binding, dependency injection, directives, and testing capabilities for robust, scalable front-end applications.

The purpose of this question is to assess the candidate’s understanding of the scope in AngularJS as a crucial execution context.

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In AngularJS, a scope is an object that refers to the application model. It acts as an execution context for expressions, serving as the intermediary between the controller and the view. Scopes are hierarchical and can watch expressions and propagate events, which makes them fundamental for data binding in AngularJS applications.

This question aims to gauge the candidate’s understanding of services in AngularJS, which are essential for maintaining clean code and reusability.

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Services in AngularJS are singleton objects or functions that are used for carrying out specific tasks. They encapsulate reusable functionalities like business logic and models, maintainable through injection into controllers, directives, and services.

The purpose of this question is to assess the candidate’s comprehension of directives in AngularJS, which are fundamental building blocks of AngularJS applications.

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Directives are markers on DOM elements (such as elements, attributes, comments or CSS classes) that tell AngularJS's HTML compiler ($compile) to attach a specified behaviour to that DOM element (e.g., via event listeners) or even to transform the DOM element and its children. Directives are powerful because they extend HTML and contribute to building reusable components.

This question aims to evaluate the candidate’s knowledge of the data binding mechanism in AngularJS, which is central to interactive applications.

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Data binding in AngularJS is the automatic synchronisation of data between the model and view components. When the model changes, the view reflects the change, and when the view changes, the model is updated as well.

The purpose of this question is to evaluate the candidate’s understanding of interpolation in AngularJS, which is a key feature for embedding expressions into HTML.

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Interpolation in AngularJS uses double curly braces ‘{{}}’ to bind data from the model to the view dynamically. It evaluates the expression within the braces and updates the HTML with the result whenever the data changes.

This question aims to assess the candidate’s ability to integrate AngularJS into HTML, which is crucial for creating interactive and dynamic web applications.

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“To integrate AngularJS with HTML, I would first add the AngularJS library to the HTML document using a ‘

The purpose of this question is to revisit the candidate's comprehensive understanding of the features that make AngularJS a powerful tool for front-end development.

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AngularJS offers two-way data binding, modular architecture, dependency injection, RESTful API handling, and deep linking for dynamic applications. These features facilitate the development of complex, high-performance web applications that are easy to manage and scale.

This question aims to test the understanding of expressions in AngularJS, which are JavaScript-like code snippets that are used mainly for data binding.

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Expressions in AngularJS are code snippets that are placed in interpolation bindings, such as {{message}}, directly in HTML templates. Unlike JavaScript expressions, they are purely data-bound and thus do not contain conditionals, loops, or exceptions.

This question aims to assess the candidate’s knowledge of filters in AngularJS, which are used to format data displayed to the user.

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Filters in AngularJS are special functions that can be added to expressions and directives to format data before displaying it in the view. Common examples include formatting dates, numbers, and arrays and even ordering data in a list.

This question aims to deepen the candidate's understanding of Dependency Injection (DI) in AngularJS, reinforcing the concept's importance in the framework's architecture.

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“In AngularJS, Dependency Injection is a robust tool that simplifies managing code dependencies between components. This feature facilitates testing by allowing components to be tested in isolation and enhances overall maintainability and configuration by decoupling the creation and use of objects. This results in cleaner, more modular code that's easier to manage and extend.”

This question evaluates candidates' understanding of data validation in AngularJS, which is critical for ensuring data integrity before processing/storage.

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“In AngularJS, I typically handle data validation using directives such as 'ng-model' and 'ng-form'. These provide built-in validation rules and states, which allow me to enforce client-side validation effectively. This ensures that form inputs comply with predefined criteria before they are submitted to the server and reliability of the data received.”

This question aims to test the candidate's knowledge of handling events in AngularJS, particularly focusing on the double-click event.

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In AngularJS, the ‘ng-dblclick’ directive allows you to specify custom behaviour on a double-click event. Double-click events are beneficial for complex interactions like field editing or opening modal dialogues, especially in interactive elements.

The purpose of this question is to assess the candidate's understanding of the Browser Object Model, which is crucial for interacting with the browser outside of the document.

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The Browser Object Model (BOM) includes objects like 'window', 'navigator', 'history', 'location', and 'screen', enabling interaction with the browser window. These objects are not part of the HTML specification but are important for controlling browser behaviour and accessing environment details, which can affect how web applications perform.

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This question evaluates the candidate's grasp of 'ng-if' and 'ng-show' directives in AngularJS, crucial for conditional rendering.

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‘ng-if’ creates or destroys elements on the DOM based on the truthiness of the expression it evaluates, providing a higher level of performance for dynamically rendered content. ‘ng-show’, on the other hand, simply changes the visibility of an element by altering its CSS styles, making it hidden or visible without removing it from the DOM.

The purpose of this question is to gauge the candidate's knowledge of the ‘$watch’ service in AngularJS, which is essential for monitoring changes in the application state.

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‘$watch’ is used in AngularJS to monitor the changes in variables or expressions. When the monitored value changes, ‘$watch’ triggers a callback function, allowing developers to perform custom actions or updates elsewhere in the application depending on the change.

This question assesses the candidate's grasp of scope hierarchy in AngularJS, which is crucial for managing data flow and event propagation.

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Scope hierarchy in AngularJS refers to the nested structure of scope objects, which mirrors the DOM architecture. Each controller and directive has its own scope, and child scopes can inherit properties and methods from their parent scopes. This hierarchical linkage allows for modular development and scope isolation, which are important for large AngularJS applications.

The purpose of this question is to evaluate the candidate’s understanding of modules in AngularJS, which are essential for separating and organising code in a maintainable manner.

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An AngularJS module defines an application. It is a container for the different parts of an application – controllers, services, filters, directives, etc. Modules declare what is needed and how components are wired together, providing a clean way to organise and bootstrap the application.

This question seeks to assess the candidate’s knowledge of the various types of directives in AngularJS and their specific applications within a project.

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Directives in AngularJS are extended HTML attributes with the prefix ‘ng-'. There are several types of directives: Attribute directives, Element directives, and CSS class directives.

The purpose of this question is to assess the candidate’s understanding of the linking function in AngularJS, which is crucial for manipulating the DOM and binding data to the template.

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The linking function in AngularJS connects the directive's scope with the HTML elements to which the directive is attached. There are two types of linking functions: pre-link and post-link. Pre-linking functions execute before the child elements are linked, while post-linking functions execute after all child elements are linked.

This question aims to test the candidate's knowledge of the injector in AngularJS, which is a key component in its dependency injection mechanism.

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The injector in AngularJS is a service locator that is used to retrieve object instances as defined by provider, instantiate types, invoke methods, and load modules. It's crucial for managing dependencies in AngularJS applications, ensuring components receive the dependencies they need to operate without needing to create them directly.

The purpose of this question is to understand how candidates perceive templates in AngularJS, which are part of the view layer within the MVC architecture.

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A template in AngularJS is HTML with additional markup. Templates are parsed by Angular and have expressions, filters, and directives that render dynamic views. These templates are directly linked to the scope and update automatically when the model data changes, promoting a reactive user interface.

This question evaluates the difference between Angular and JavaScript expressions, which is crucial for accurate logic in AngularJS applications.

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Angular expressions are similar to JavaScript expressions but are more focused on binding data to HTML. They do not support conditionals, loops, or exceptions, and they are always evaluated within the context of Angular's scope. JavaScript expressions. On the other hand, have full language capabilities and run in the standard JavaScript context.

The purpose of this question is to assess the candidate’s understanding of DI in AngularJS, which is a core feature for managing dependencies within the application.

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Dependency Injection is a design pattern in which a component or object receives its dependencies from an external source rather than creating them internally. In AngularJS, DI is implemented through an injector subsystem, which is responsible for creating components, resolving their dependencies, and providing them to other components as needed.

This question aims to evaluate the candidate’s ability to create and apply custom filters in AngularJS, which are essential for extending the framework to suit specific needs.

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Custom filters in AngularJS can be defined as performing specific text transformations or data manipulations that are not covered by the standard filters. For instance, a custom filter could be created to reverse the order of characters in a string. This is implemented by registering a new filter factory function that processes the input data and returns the transformed output.

The purpose of this question is to assess the candidate's understanding of the currency filter in AngularJS, which is used to format number inputs as currency values.

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The currency filter in AngularJS formats a number to a currency format, including the currency symbol and appropriate decimal places. It formats currency values with specified symbols and decimal places, which is suitable for financial applications.

This question aims to assess the candidate's grasp of AngularJS's scope hierarchy and the differences between $rootScope and $scope.

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$rootScope in AngularJS is the parent scope for all other scopes in an application, providing global scope properties and methods. $rootScope properties are global and accessible throughout the app, whereas $scope properties are confined to a controller and its view.

The purpose of this question is to assess the candidate’s knowledge of the injector in AngularJS, a fundamental component of the dependency injection system.

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“The injector is a service in AngularJS that is responsible for resolving dependencies of components, such as services, filters, and directives. The injector maintains a container of service instances that it reuses, providing a single instance of each service per application.”

This question aims to assess the candidate's grasp of scope hierarchy in AngularJS and its impact on data flow and event handling.

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AngularJS applications can have multiple scopes, as scopes in AngularJS are arranged in a hierarchical structure similar to the DOM. There is typically one root scope, and each controller or directive can create child scopes. This hierarchical structure helps in isolating scopes in different parts of the application, thereby managing the scope's visibility and life cycle efficiently.

This question seeks to assess the candidate's familiarity with logging in AngularJS, which is crucial for debugging and tracking application behaviour.

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Logging in AngularJS is primarily handled through the ‘$log’ service, which provides simple logging functionality similar to console methods (like ‘console.log’, ‘console.error’, etc.). Developers inject ‘$log’ into controllers or services for logging and outputting debug info to the browser's console.

The purpose of this question is to evaluate the candidate's understanding of array handling functions in AngularJS, focusing on ‘findIndex’.

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The ‘findIndex’ function in AngularJS is used to locate the index of the first element in an array that satisfies a specific condition provided in a callback function. If no element satisfies the condition, ‘findIndex’ returns -1, indicating that no valid index was found.

The purpose of this question is to assess the candidate’s understanding of routing in AngularJS, which is pivotal for building single-page applications.

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The `$routeProvider` in AngularJS is used to configure routes within an application. It enables URL linking to specific views and controllers, allowing the application to maintain a state through URL changes. This is essential for single-page applications where different views are loaded dynamically based on user interaction and URL changes.

The purpose of this question is to evaluate the candidate’s ability to manage cookies in AngularJS, which is important for maintaining state and user sessions.

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“In AngularJS, I manage cookies using the `$cookies` service. To set a cookie, I use `$cookies.put('key', 'value') `; to retrieve one, I use `$cookies.get('key') `; and to delete a cookie, I employ `$cookies.remove('key') `. This functionality is essential for handling session data and user preferences in web applications, ensuring a smooth and tailored user experience.”

This question seeks to assess the candidate's understanding of the service creation method in AngularJS, which is fundamental for encapsulating reusable business logic. 

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The service method in AngularJS is a way to create reusable and injectable services using a constructor function. When defining a service, AngularJS instantiates it with the ‘new’ keyword, and the resulting object is used throughout the application. This method is ideal for cases where complex business logic needs to be encapsulated within an injectable service.

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The purpose of this question is to test the candidate’s knowledge of dependency injection in AngularJS, focusing on what components can be injected.

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In AngularJS, various components can be injected as dependencies, including services, factories, controllers, filters, and directives. This allows for modular code that can be easily tested and maintained.

This question aims to assess the candidate's familiarity with AngularJS Global API functions, which are utilities that can be used throughout AngularJS applications.

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AngularJS provides several Global API functions that are useful for various tasks, such as ‘angular.isString()’, ‘angular.isArray()’, ‘angular.extend()’, ‘angular.copy()’, and ‘angular.forEach()’. These functions help in handling common JavaScript tasks such as checking variable types, extending objects, and iterating over objects and arrays.

This question assesses understanding of ‘$rootScope’ in AngularJS, a fundamental component in AngularJS scope hierarchy.

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‘$rootScope’ is the top-level scope object in AngularJS, which all other scopes inherit. It is accessible in the entire application, making it a powerful way to share data and events across different controllers and directives. However, it should be used sparingly to avoid polluting the global namespace and to maintain modular and maintainable code.

This question aims to assess the candidate’s practical knowledge of implementing ‘ng-view’ in Angular, which is essential for configuring views in single-page applications.

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’ng-view’ is a directive in Angular that acts as a placeholder where a corresponding view (HTML + controller) will be placed based on the configured route. It is typically used in combination with the ‘$routeProvider’ to define which view to display based on the URL.

In this example, ‘ng-view’ dynamically loads either ‘home.html’ or ‘about.html’ into the placeholder, depending on the current path in the URL, managed by Angular's routing mechanism.

The purpose of this question is to evaluate the candidate's practical programming skills in AngularJS, focusing on event handling and DOM manipulation.

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To hide an HTML tag with a button, click in AngularJS; you can use the ‘ng-click’ directive to bind a click event to a function that toggles a Boolean scope variable and ‘ng-show’ or ‘ng-hide’ to conditionally display the HTML tag based on the state of the Boolean variable. For example:

Html code:

Javascript code:

The purpose of this question is to evaluate the candidate's understanding of the factory method in AngularJS, which is essential for creating reusable services within an application.

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The factory method in AngularJS defines a service returning an object with methods and properties, facilitating injection and reuse across the app. By defining a function generating this object, it encapsulates functionalities for clean, modular code, separating concerns effectively.

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