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Angular2 data binding example

What is Angular 2 Pipes?

What is Pipes?

“Pipes transform displayed values within a template.”

Sometimes, the data is not displays in the well format on the template that time where using pipes.
You also can execute a function in the template to get its returned value.

The angular 2 have some additional pipes names that are async, decimal, percept and so on. And also some of pipes not supported in angular 2 that are number, orderBy and filter and these are archiving using “custom pipes”.

Key Points:-
Pipe class implements the “PipeTransform” interfaces transform method that accepts an input value and returns the transformed result.

There will be one additional argument to the transform method for each parameter passed to the pipe.

The “@Pipe” decorator allows us to define the pipe name that is globally available for use in any template in the across application.

For example as,

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

@Pipe({
    name: 'barcode',
    pure: false
})
export class BarCodePipe implements PipeTransform {
    transform(value: string, args: any[]): string {
        if (!value) {
            return '';
        }
        return "****-****_" + (value.length > 8 ? (value.length - 8): '')
    }
}

What is a pure and impure pipe?
In Angular 2, there are two types of pipes i.e.
1.      pure
2.      impure

The pure pipe is by default. Every pipe has been pure by default. If you want to make a pipe impure that time you will allow the setting pure flag to false.

Pure Pipes:-
Angular executes a pure pipe only when it detects a pure change to the input value. A pure change can be primitive or non-primitive.

Primitive data are only single values, they have not special capabilities and the non-primitive data types are used to store the group of values.

For example for pipe pure,
import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
    name: 'barcode'
})
export class BarCodePipe implements PipeTransform {
    transform(value: string, args: any[]): string {
        if (!value) {
            return '';
        }
        return "****-****_" + (value.length > 8 ? (value.length - 8): '')
    }
}

Impure Pipes:-
Angular executes an impure pipe during every component change detection cycle. An impure pipe is called often, as often as every keystroke or mouse-move.

If you want to make a pipe impure that time you will allow the setting pure flag to false.

For example for pipe impure,
import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
    name: 'barcode',
    pure: false
})
export class BarCodePipe implements PipeTransform {
    transform(value: string, args: any[]): string {
        if (!value) {
            return '';
        }
        return "****-****_" + (value.length > 8 ? (value.length - 8): '')
    }

}

Angular 2 Built-in Pipes:-
1.      DatePipe,
2.      UpperCasePipe,
3.      LowerCasePipe,
4.      CurrencyPipe,
5.      PercentPipe,
6.      JsonPipe,
7.      AsyncPipe,
8.      And so on..


The following table shows a comparison between Angular 1.x and Angular 2.

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