Angular Interview Question Set 2

Categories: Angular

What is an AOT compilation? What are its advantages?

The Ahead-of-time (AOT) compiler converts the Angular HTML and TypeScript code into JavaScript code during the build phase, i.e., before the browser downloads and runs the code.

Some of its advantages are as follows. 

1. Faster rendering

2. Fewer asynchronous requests

3. Smaller Angular framework download size

4. Quick detection of template errors

5. Better security



What are Components in Angular?

Components are the basic building blocks of the user interface in an Angular application. Every component is associated with a template and is a subset of directives. An Angular application typically consists of a root component, which is the AppComponent, that then branches out into other components creating a hierarchy.



What are Pipes in Angular? 

Pipes are simple functions designed to accept an input value, process, and return as an output, a transformed value in a more technical understanding. Angular supports several built-in pipes. However, you can also create custom pipes that cater to your needs. 

Some key features include: 

  1. Pipes are defined using the pipe “|” symbol. 
  2. Pipes can be chained with other pipes.
  3. Pipes can be provided with arguments by using the colon (:) sign.


What is the PipeTransform interface?

As the name suggests, the interface receives an input value and transforms it into the desired format with a transform() method. It is typically used to implement custom pipes.

import { Pipe, PipeTransform } from '@angular/core';


@Pipe({


  name: 'demopipe'


})

export class DemopipePipe implements PipeTransform {


  transform(value: unknown, ...args: unknown[]): unknown {


    return null;

  }


What are Pure Pipes? 

These pipes are pipes that use pure functions. As a result of this, a pure pipe doesn't use any internal state, and the output remains the same as long as the parameters passed stay the same. Angular calls the pipe only when it detects a change in the parameters being passed. A single instance of the pure pipe is used throughout all components. 


What are Impure Pipes?

For every change detection cycle in Angular, an impure pipe is called regardless of the change in the input fields. Multiple pipe instances are created for these pipes. Inputs passed to these pipes can be mutable. 

By default, all pipes are pure. However, you can specify impure pipes using the pure property, as shown below.

@Pipe({

  name: 'demopipe',

  pure : true/false 

})

export class DemopipePipe implements PipeTransform {



 What is an ngModule?

NgModules are containers that reserve a block of code to an application domain or a workflow. @NgModule takes a metadata object that generally describes the way to compile the template of a component and to generate an injector at runtime. In addition, it identifies the module's components, directives, and pipes, making some of them public, through the export property so that external components can use them.


 What are filters in Angular? Name a few of them.

Filters are used to format an expression and present it to the user. They can be used in view templates, controllers, or services. Some inbuilt filters are as follows. 

  1. date - Format a date to a specified format.
  2. filter - Select a subset of items from an array.
  3. Json - Format an object to a JSON string.
  4. limitTo -  Limits an array/string, into a specified number of elements/characters.
  5. lowercase - Format a string to lowercase.



What is view encapsulation in Angular?

View encapsulation defines whether the template and styles defined within the component can affect the whole application or vice versa. Angular provides three encapsulation strategies:

  1. Emulated - styles from the main HTML propagate to the component.
  2. Native - styles from the main HTML do not propagate to the component. 
  3. None - styles from the component propagate back to the main HTML and therefore are visible to all components on the page.

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