Angular Interview Question | Pipes

 

In Angular, pipes are a feature that allows us to transform the data. Using Pipes we can format, filter, and manipulate data. Angular supports several built-in pipes. However, we can also create custom pipes based on our requirements

Key Features:

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

Ex.

Built-in Pipes: Angular comes with several built-in pipes that cover common transformation tasks. Some examples include:

• {{ someDate        | date:'longDate' }}              — Formats a date as a long date.
• {{ someText        | uppercase }}                      — Converts text to uppercase. 
• {{ someNumber  | currency:'USD':true }}      — Formats a number as currency (USD) with a                                                                                     currency symbol.

Chaining Pipes: You can chain multiple pipes together to perform multiple transformations in sequence.  

         Ex : 

                        

In this example, the text will be converted to uppercase first and then only the first 10 characters will be displayed

PipeTransform interface : The PipeTransform interface is used when we creating custom pipes in Angular.  

       Ex.     

The PipeTransform interface contains a single method: transform. This method is where you define the transformation logic for your custom pipe. It takes two parameters:

1.  value: This is the input data that you want to transform using the pipe.
2.  ...args: These are optional parameters that you can use to pass additional information to the pipe.

Ex.

Pure Pipes vs Impure Pipes :   Pure pipes are designed to optimize change detection by only recalculating when the input values or arguments change. If the input values remain the same, the pipe won't run its transform method, reducing unnecessary calculations. 

 Impure pipes don't optimize change detection and will run their transform method every time there's a change detected anywhere in the application.

Aspect	Pure Pipes	Impure Pipes
Change Detection Optimization	Pure pipes optimize change detection by only recalculating when input values or arguments change.	Impure pipes do not optimize change detection and always recalculate on every change detection cycle.
Performance	Pure pipes are more efficient for static and predictable data as they avoid unnecessary recalculations.	Impure pipes may lead to more recalculations, impacting performance, especially if used extensively.
Use Cases	Suitable for deterministic transformations, like formatting, calculations, and filtering, where input data remains unchanged.	Suitable for scenarios involving dynamic data, real-time updates, and side effects, where frequent recalculations are needed.
Syntax	To define a pure pipe, set the pure property to true in the @Pipe decorator.	Impure pipes are the default behavior when you create a custom pipe without specifying the pure property.

Create the Pure Pipe :

Ex. 

Create the Impure Pipe :

Ex.  

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Angular Ivy

                                                Angular Ivy

Angular Ivy is a new rendering engine that was introduced in Angular version 9. It is designed to provide better performance and reduce the size of the generated code. Ivy is a significant improvement over the previous rendering engine, known as View Engine.

The main advantage of Angular Ivy is its ability to generate smaller bundle sizes. This is achieved through improved tree shaking, which removes any unused code from the final bundle. This helps to reduce the amount of data that needs to be downloaded by the client, leading to faster load times and better performance.

In addition to smaller bundle sizes, Ivy also provides better support for lazy loading. Lazy loading is a technique that loads only the parts of an application that are needed, rather than loading the entire application at once. This can help to improve the performance of the application, particularly on slower connections.

Another important feature of Angular Ivy is its support for incremental compilation. This means that the compiler only recompiles the parts of the application that have changed, rather than recompiling the entire application. This can help to reduce the amount of time it takes to build and deploy the application.

Ivy also introduces a number of improvements to the template compiler. For example, it allows for faster compilation times, as well as improved error messages and debugging tools. This can help to make it easier for developers to identify and fix issues in their code.

Finally, Angular Ivy provides a number of performance improvements when rendering components. For example, it reduces the amount of memory required to render components, and improves the efficiency of change detection. This can help to improve the overall performance of the application, particularly on larger applications with many components.

Overall, Angular Ivy is a significant improvement over the previous rendering engine in Angular. Its ability to generate smaller bundle sizes, support lazy loading, and provide better performance make it a valuable addition to the Angular framework. Developers who are looking to improve the performance and maintainability of their Angular applications should consider using Ivy in their projects.

Here is an example of how Angular Ivy can be used in an application, along with some sample code:

1. First, make sure that your Angular project is using version 9 or higher. You can check your version by running the following command in the terminal:

ng version

2. To enable Ivy, set the "enableIvy" property in the "angularCompilerOptions" section of your "tsconfig.json" file to true:

{ "compilerOptions": { "enableIvy": true } }

3. Now that Ivy is enabled, you can take advantage of some of its features, such as improved performance and smaller bundle sizes. Here is some sample code that demonstrates how Ivy can be used to optimize a component:

import { Component, Input } from '@angular/core'; @Component({ selector: 'my-component', template: ` <div *ngFor="let item of items"> {{ item }} </div> `, }) export class MyComponent { @Input() items: string[]; }

In this component, we are using the "ngFor" directive to loop over an array of items and display them in a list. To optimize this component using Ivy, we can use the "trackBy" function to tell Angular how to track changes in the list:

import { Component, Input, TrackByFunction } from '@angular/core'; @Component({ selector: 'my-component', template: ` <div *ngFor="let item of items; trackBy: trackByFn"> {{ item }} </div> `, }) export class MyComponent { @Input() items: string[]; trackByFn: TrackByFunction<string> = (index, item) => item; }

In this updated component, we are using the "trackBy" function to tell Angular to track changes in the list based on the items themselves, rather than their position in the list. This can help to improve performance by reducing the amount of DOM manipulation that needs to be done when the list changes.

This is just one example of how Angular Ivy can be used to optimize an application. As you can see, Ivy provides developers with powerful tools for improving the performance and maintainability of their Angular applications.