Cognizant Angular Frontend Developer Interview Questions, Process, and Tips

Q1. How directives are different from component
Ans. 
Directives are used to add behavior to existing DOM elements, while components are used to create new custom elements.
• Directives are used to manipulate the behavior of existing DOM elements, such as changing their appearance or adding event listeners.

• Components are used to create custom elements with their own templates, styles, and behavior.

• Directives can be structural (like ngIf and ngFor) or attribute-based (like ng...read more
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Q2. What is hoisting
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.
• Variable and function declarations are hoisted to the top of their scope, regardless of where they are declared in the code.

• Only the declarations are hoisted, not the initializations.

• Function declarations are hoisted before variable declarations.
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Q1. Explain design patterns.
Ans. 
Design patterns are reusable solutions to common problems in software design.
• Design patterns help in creating maintainable, scalable, and efficient code.

• They provide a common language for developers to communicate about solutions to recurring problems.

• Examples of design patterns include Singleton, Factory, Observer, and Strategy patterns.
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Q2. Explain subject. what is replay subject
Ans. 
ReplaySubject is a type of Subject in RxJS that records multiple values and replays them to new subscribers.
• ReplaySubject is a type of Subject in RxJS

• It records multiple values and replays them to new subscribers

• It has a buffer size that determines how many values to replay
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Q1. Salary discussion
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Q1. What are the time queue, etc in API
Ans. 
Time queue in API refers to managing requests in a sequential order.
• Time queue ensures that API requests are processed in the order they are received.

• It helps in preventing overload on the server by limiting the number of concurrent requests.

• Examples include using promises or async/await in JavaScript to handle API calls sequentially.
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Q2. What is the meaning of preflight in API? (All questions are related to dev oops profile. I applied for Angular)
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Q1. What is lazy loading and how can we achieve this?
Ans. 
Lazy loading is a technique used to defer loading of non-essential resources until they are actually needed.
• Lazy loading helps improve the initial loading time of a web application by only loading essential resources upfront.

• In Angular, lazy loading is achieved by creating separate modules for different parts of the application and loading them on demand.

• Lazy loading can be implemented using the loadChildren property i...read more
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Q2. Difference between in constructor and NgOninit()?
Ans. 
Constructor is used to initialize class properties, NgOnInit() is a lifecycle hook used to perform initialization after Angular has initialized the component.
• Constructor is a TypeScript feature used to create and initialize class properties.

• NgOnInit() is an Angular lifecycle hook that is called after Angular has initialized the component.

• Constructor is called before NgOnInit() during component initialization.

• Example: C...read more
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Q3. What is two-way binding?
Ans. 
Two-way binding is a feature in Angular that allows automatic synchronization of data between the model and the view.
• Two-way binding allows changes in the model to be reflected in the view and vice versa

• It simplifies the process of updating the UI based on user input or changes in the data model

• Example: Using ngModel directive in Angular forms to bind input fields to model properties
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Q4. Difference between Observable and Promise
Ans. 
Observable is a stream that allows multiple values over time, while Promise is a single value that resolves or rejects.
• Observable can handle multiple values over time, while Promise can only handle a single value.

• Observable is lazy, meaning it won't execute until it is subscribed to, while Promise is eager and executes immediately.

• Observable is cancellable, allowing you to unsubscribe, while Promise is not cancellable ...read more
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Q5. What is a pipe in angular and its types
Ans. 
A pipe in Angular is used to transform data before displaying it in the template.
• Pipes are used in templates to format data before displaying it to the user

• There are built-in pipes like DatePipe, UpperCasePipe, LowerCasePipe, etc.

• Custom pipes can also be created by implementing the PipeTransform interface

• Pipes can be chained together to perform multiple transformations on the data
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