Angular - Interview Questions and Answers for 'Angular' | Search Interview Question

Angular - Interview Questions and Answers for 'Angular' - 67 question(s) found - Order By Rating

Q1. Can we have a directive that get's applied based on an attribute on a field ?

Angular

Ans. Yes

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Q2. How can we add a particular styling to a field based on a condition ?

Angular

Ans. We can create a directive to do that.

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Q3. What is the use of ElementRef in angular ?

Angular

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Q4. What is the use of Renderer class in angular ?

Angular

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Q5. What is the use of NgControl ?

Angular

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Q6. Can we have multiple selectors for a directive in Angular ?

Angular

Ans. Yes

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Q7. How can we add a text in front of all input fields in an application ?

Angular

Ans. We can create a directive with selector as 'input' and then onInit of the directive , we can append the text to the input control html.

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Q8. Can we get the validators for a control in angular ? How ?

Angular

Ans. No - https://github.com/angular/angular/issues/13461

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Q9. How can you trim all strings in an array ?

Ans. array.map(s => s.trim())

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Q10. What does this warning message for the unit test means

WARN: 'Spec has no expectations.'

Angular

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Q11. How can we sort an observable of a user array on user name ( name being one of the field of user ) ?

RxJs

Ans. userArrayObservable.pipe(
map(userArray => {
return userArray.sort(comparator);
});
)

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Q12. Can we specify multiple maps within pipe ?

RxJs

Ans. Yes, it's same as passing multiple methods within pipe. Output of one map is passed to second and so on.

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Q13. Can we specify multiple functions in the pipe ? What happens if we do it ?

RxJs

Ans. Yes, We can specify multiple functions within pipe method. In that case first function get's called with the observable , the response if then passed to the second method and so on.

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Q14. Why do we do transformation on the observable itself rather than doing it in the subscriber ?

RxJs

Ans. Because that way we just need to do that transformation at one place and not within each subscriber. Single source of truth.

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Q15. What do we specify within the pipe method ?

RxJs

Ans. Operator function to which an observable is passed for transformation.

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Q16. What does pipe does on an observable ?

RxJs

Ans. With pipe we specify the operator function to which this observable is passed for transforming the observable.

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Q17. What is the difference between Subject and Observable ?

Angular

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Q18. What is the difference between subscribe and unsubscribe ?

Angular

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Q19. What is the difference between subscribe and emit ?

Angular

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Q20. Have you ever faced problem because of some listener / observers / subscriber performing action on the subscription which you don't want ? How did you fix the problem ?

Angular

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Q21. What is the difference between closing and completing the observer / listener ?

Angular

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Q22. How can print the whole object state in the console in javascript ?

Javascript

Ans. We can JSON.stringify

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Q23. Can you please share best practices while designing an angular application ?

Angular

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Q24. What are the benefits of using UI framework like Angular , View js etc instead of plain vanilla js and html ?

Javascript

Ans. These frameworks facilitates easier product development and enhancement and maintainability by having separation of concerns ( using oops ) and helps in development of reusable libraries / components. So in nutshell , they make development and maintenance of large scale application easier.

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Q25. Have you ever had any problem with asynchronous programming due to race condition ?

Angular

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Q26. What is interpolation in Angular ?

Angular

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Q27. What is a component decorator ?

Angular

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Q28. What are the different conditions that triggers view update in case of push ChangeDetectionStrategy ?

Angular

Ans. 1. Any change in Input
2. Any even originating from the component or it's child components
3. Explicit trigger

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Q29. Which change detection strategy do you use in your application and Why ?

Angular

Ans. We use ChangeDetectionStrategy.Push

As the application grows bigger , The default change detection strategy could become a performance overhead and hence should be avoided.

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Q30. Difference between ViewChild and ContentChild.

Angular

Ans. Any directive, component, and element which is part of component template is accessed as ViewChild. Whereas, any element or component which is projected inside is accessed as ContentChild.

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