[angular] Angular - Use pipes in services and components

In AngularJS, I am able to use filters (pipes) inside of services and controllers using syntax similar to this:

$filter('date')(myDate, 'yyyy-MM-dd');

Is it possible to use pipes in services/components like this in Angular?

Yes, it is possible by using a simple custom pipe. Advantage of using custom pipe is if we need to update the date format in future, we can go and update a single file.

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

@Pipe({
    name: 'dateFormatPipe',
})
export class dateFormatPipe implements PipeTransform {
    transform(value: string) {
       var datePipe = new DatePipe("en-US");
        value = datePipe.transform(value, 'MMM-dd-yyyy');
        return value;
    }
}

{{currentDate | dateFormatPipe }}

You can always use this pipe anywhere , component, services etc

For example:

export class AppComponent {
  currentDate : any;
  newDate : any;
  constructor(){
    this.currentDate = new Date().getTime();
    let dateFormatPipeFilter = new dateFormatPipe();
    this.newDate = dateFormatPipeFilter.transform(this.currentDate);
    console.log(this.newDate);
}

Don't forget to import dependencies.

import { Component } from '@angular/core';
import {dateFormatPipe} from './pipes'

Custom Pipe examples and more info

If you want to use your custom pipe in your components, you can add

@Injectable({
  providedIn: 'root'
})

annotation to your custom pipe. Then, you can use it as a service

Other answers don't work in angular 5?

I got an error because DatePipe is not a provider, so it cannot be injected. One solution is to put it as a provider in your app module but my preferred solution was to instantiate it.

Instantiate it where needed:

I looked at DatePipe's source code to see how it got the locale: https://github.com/angular/angular/blob/5.2.5/packages/common/src/pipes/date_pipe.ts#L15-L174

I wanted to use it within a pipe, so my example is within another pipe:

    import { Pipe, PipeTransform, Inject, LOCALE_ID } from '@angular/core';
    import { DatePipe } from '@angular/common';

    @Pipe({
        name: 'when',
    })
    export class WhenPipe implements PipeTransform {
        static today = new Date((new Date).toDateString().split(' ').slice(1).join(' '));
        datePipe: DatePipe;

        constructor(@Inject(LOCALE_ID) private locale: string) {
            this.datePipe = new DatePipe(locale);
        }
        transform(value: string | Date): string {
            if (typeof(value) === 'string')
                value = new Date(value);

            return this.datePipe.transform(value, value < WhenPipe.today ? 'MMM d': 'shortTime')
        }
    }

The key here is importing Inject, and LOCALE_ID from angular's core, and then injecting that so you can give it to the DatePipe to instantiate it properly.

Make DatePipe a provider

In your app module you could also add DatePipe to your providers array like this:

    import { DatePipe } from '@angular/common';

    @NgModule({
        providers: [
            DatePipe
        ]
    })

Now you can just have it injected in your constructor where needed (like in cexbrayat's answer).

Summary:

Either solution worked, I don't know which one angular would consider most "correct" but I chose to instantiate it manually since angular didn't provide datepipe as a provider itself.

As of Angular 6 you can import formatDate from @angular/common utility to use inside the components.

It was intruduced at https://github.com/smdunn/angular/commit/3adeb0d96344c15201f7f1a0fae7e533a408e4ae

I can be used as:

import {formatDate} from '@angular/common';
formatDate(new Date(), 'd MMM yy HH:mm', 'en');

Although the locale has to be supplied

If you don't want do 'new myPipe()' because you're injecting dependencies to pipe, you can inject in component like provider and use without new.

Example:

    // In your component...

    import { Component, OnInit } from '@angular/core';
    import { myPipe} from './pipes';

    @Component({
      selector: 'my-component',
      template: '{{ data }}',
      providers: [ myPipe ]
    })
    export class MyComponent() implements OnInit {
      data = 'some data';
      constructor(private myPipe: myPipe) {}

      ngOnInit() {
        this.data = this.myPipe.transform(this.data);
      }
    }

You can use formatDate() to format the date in services or component ts. syntax:-

    formatDate(value: string | number | Date, format: string, locale: string, timezone?: string): string

import the formatDate() from common module like this,

    import { formatDate } from '@angular/common';

and just use it in the class like this ,

    formatDate(new Date(), 'MMMM dd yyyy', 'en');

You can also use the predefined format options provided by angular like this ,

    formatDate(new Date(), 'shortDate', 'en');

You can see all other predefined format options here ,

https://angular.io/api/common/DatePipe

This answer is now outdated

recommend using DI approach from other answers instead of this approach

Original answer:

You should be able to use the class directly

new DatePipe().transform(myDate, 'yyyy-MM-dd');

For instance

var raw = new Date(2015, 1, 12);
var formatted = new DatePipe().transform(raw, 'yyyy-MM-dd');
expect(formatted).toEqual('2015-02-12');