Pipes

Introduction#

Pipes are very similar to filters in AngularJS in that they both help to transform the data into a specified format.The pipe character | is used to apply pipes in Angular.

Custom Pipes

my.pipe.ts

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

@Pipe({name: 'myPipe'})
export class MyPipe implements PipeTransform {

  transform(value:any, args?: any):string {
    let transformedValue = value; // implement your transformation logic here
    return transformedValue;
  }

}

my.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'my-component',
  template: `{{ value | myPipe }}`
})
export class MyComponent {

    public value:any;

}

my.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { MyComponent } from './my.component';
import { MyPipe } from './my.pipe';

@NgModule({
  imports: [
    BrowserModule,
  ],
  declarations: [
    MyComponent,
    MyPipe
  ],
})
export class MyModule { }

Multiple custom pipes

Having different pipes is a very common case, where each pipe does a different thing. Adding each pipe to each component may become a repetitive code.

It is possible to bundle all frequently used pipes in one Module and import that new module in any component needs the pipes.

breaklines.ts

import { Pipe } from '@angular/core';
/**
 * pipe to convert the \r\n into <br />
 */
@Pipe({ name: 'br' })
export class BreakLine {
    transform(value: string): string {
        return value == undefined ? value : 
             value.replace(new RegExp('\r\n', 'g'), '<br />')
              .replace(new RegExp('\n', 'g'), '<br />');
    }
}

uppercase.ts

import { Pipe } from '@angular/core';
/**
 * pipe to uppercase a string
 */
@Pipe({ name: 'upper' })
export class Uppercase{
    transform(value: string): string {
        return value == undefined ? value : value.toUpperCase( );
    }
}

pipes.module.ts

import { NgModule } from '@angular/core';
import { BreakLine } from './breakLine';
import { Uppercase} from './uppercase';

@NgModule({
    declarations: [
        BreakLine,
        Uppercase
    ],
    imports: [

    ],
    exports: [
        BreakLine,
        Uppercase
    ]
    ,
})
export class PipesModule {}

my.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'my-component',
  template: `{{ value | upper | br}}`
})
export class MyComponent {

    public value: string;

}

my.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { MyComponent } from './my.component';
import { PipesModule} from './pipes.module';

@NgModule({
  imports: [
    BrowserModule,
    PipesModule,
  ],
  declarations: [
    MyComponent,
  ],
})