Tutorial Create Angular 4 Currency Format Directive For Textbox

Angular 4 tutorial how to create currency directive. Lately, I am studying about angular 4 because there is an ERP project in the company where I work. Creating a currency formatter on the angular is different from the JQuery I’ve discussed in the How to Create Jquery Plugin for Input Currency article. But if you’re used to Angular 4, making currency directive is pretty easy, and the use is more efficient than jquery. Consider the following tutorial.

This simple directive is used to identify input field with the custom currency format. To create a currency format in the input field requires directive and pipe on angular 4. This article will create a custom currency like the following gif image

Before starting the main topic, I will discuss a bit about what is directive and why we need a pipe?

# Directive

An angular directive is a function executed by Angular when Angular finds Directive in DOM (Document Object Model), the function can almost do everything like hiding element before the page loaded, repeat, execute an expression, etc.

There are two types of directive: built-in directive and custom directive. To create this angular directive in the text field, we need a custom directive.

# Pipe

The pipes are similar to Filters in AngularJs (Angular 1). The pipe is used to format output on HTML templates. Angular 4 also provides built-in pipe such as uppercase, lowercase, currency, Datepipe. In this tutorial, we will create a custom pipe so that the currency format can run well.

Features angular currency input that we will build

Only number in input typetext
When element does not get focus/blur, display value in input box will become format currency
When the element gets the focus, the formatted currency in the text field will disappear
When the element gets the focus, all the values in the text box will be selected

Tutorial Angular 4 Format Currency In Inputs Value In Angular 4

Note: In the following example I will create a simple directive for Indonesian format currency (Rupiah)

Make a custom directive and a custom pipe

# Custom Pipe

Create a new pipe using an angular-cli with the following command

ng g pipe pipe/mycurrency

1	ng g pipe pipe/mycurrency

Edit mycurrency.pipe.ts and copy the following code

import { Pipe, PipeTransform } from '@angular/core';
const padding = "000000";

@Pipe({
  name: 'mycurrency'
})
export class MycurrencyPipe implements PipeTransform {
  private prefix: string;
  private decimal_separator:string;
  private thousands_separator:string;
  private suffix:string;

  constructor(){
    this.prefix='Rp.';
    this.suffix='';
    this.decimal_separator='.';
    this.thousands_separator = ',';
  }
  transform(value: string, fractionSize:number = 0 ): string {
    
    if(parseFloat(value) % 1 != 0)
    {
      fractionSize = 2;
    }
    let [ integer, fraction = ""] = (parseFloat(value).toString() || "").toString().split(".");

    fraction = fractionSize > 0
      ? this.decimal_separator + (fraction+padding).substring(0, fractionSize) : "";
    integer = integer.replace(/\B(?=(\d{3})+(?!\d))/g, this.thousands_separator);
    if(isNaN(parseFloat(integer)))
    {
          integer = "0";
    }
      return this.prefix + integer + fraction + this.suffix;
    
  }

  parse(value: string, fractionSize: number = 2): string {
    let [ integer, fraction = "" ] = (value || "").replace(this.prefix, "")
                                                  .replace(this.suffix, "")
                                                  .split(this.decimal_separator);

    integer = integer.replace(new RegExp(this.thousands_separator, "g"), "");

    fraction = parseInt(fraction, 10) > 0 && fractionSize > 0
      ? this.decimal_separator + (fraction + padding).substring(0, fractionSize)
      : "";

    return integer + fraction;
  }

}

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

const padding = "000000";

@Pipe({

name: 'mycurrency'

})

export class MycurrencyPipe implements PipeTransform {

private prefix: string;

private decimal_separator:string;

private thousands_separator:string;

private suffix:string;

constructor(){

this.prefix='Rp.';

this.suffix='';

this.decimal_separator='.';

this.thousands_separator = ',';

}

transform(value: string, fractionSize:number = 0 ): string {

if(parseFloat(value) % 1 != 0)

{

fractionSize = 2;

}

let [ integer, fraction = ""] = (parseFloat(value).toString() || "").toString().split(".");

fraction = fractionSize > 0

? this.decimal_separator + (fraction+padding).substring(0, fractionSize) : "";

integer = integer.replace(/\B(?=(\d{3})+(?!\d))/g, this.thousands_separator);

if(isNaN(parseFloat(integer)))

{

integer = "0";

}

return this.prefix + integer + fraction + this.suffix;

}

parse(value: string, fractionSize: number = 2): string {

let [ integer, fraction = "" ] = (value || "").replace(this.prefix, "")

.replace(this.suffix, "")

.split(this.decimal_separator);

integer = integer.replace(new RegExp(this.thousands_separator, "g"), "");

fraction = parseInt(fraction, 10) > 0 && fractionSize > 0

? this.decimal_separator + (fraction + padding).substring(0, fractionSize)

: "";

return integer + fraction;

}

# Custom Directive

Create a new directive using an angular cli with the following command

ng g directive directive/mycurrency

1	ng g directive directive/mycurrency

Edit mycurrency.directive.ts and copy the following code

import { Directive, HostListener, ElementRef, OnInit } from '@angular/core';
import {MycurrencyPipe} from '../pipe/mycurrency.pipe';
@Directive({
  selector: '[appMycurrency]'
})
export class MycurrencyDirective implements OnInit{
  private el: any;

  constructor(
    private elementRef:ElementRef,
    private formatcurrencypipe:MycurrencyPipe
  ) { 
    this.el = this.elementRef.nativeElement;
  }
  ngOnInit(){
    this.el.value = this.formatcurrencypipe.transform(this.el.value);
  }
  @HostListener("focus",["$event.target.value","$event"])
  onFocus(value,event) {
    this.el.value = this.formatcurrencypipe.parse(value); // opossite of transform
    if(event.which== 9)
    {
        return false;
    }
    this.el.select();
    
  }

  @HostListener("blur", ["$event.target.value"])
  onBlur(value) {
    this.el.value = this.formatcurrencypipe.transform(value);
  }
  @HostListener('keydown', ['$event']) onKeyDown(event) {
    let e = <KeyboardEvent> event;
      if ([46, 8, 9, 27, 13, 110, 190].indexOf(e.keyCode) !== -1 ||
        // Allow: Ctrl+A
        (e.keyCode === 65 && (e.ctrlKey || e.metaKey)) ||
        // Allow: Ctrl+C
        (e.keyCode === 67 && (e.ctrlKey || e.metaKey)) ||
        // Allow: Ctrl+V
        (e.keyCode === 86 && (e.ctrlKey || e.metaKey)) ||
        // Allow: Ctrl+X
        (e.keyCode === 88 && (e.ctrlKey || e.metaKey)) ||
        // Allow: home, end, left, right
        (e.keyCode >= 35 && e.keyCode <= 39)) {
          // let it happen, don't do anything
          return;
        }
        // Ensure that it is a number and stop the keypress
        if ((e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) && (e.keyCode < 96 || e.keyCode > 105)) {
            e.preventDefault();
        
      }
  }

}

import { Directive, HostListener, ElementRef, OnInit } from '@angular/core';

import {MycurrencyPipe} from '../pipe/mycurrency.pipe';

@Directive({

selector: '[appMycurrency]'

})

export class MycurrencyDirective implements OnInit{

private el: any;

constructor(

private elementRef:ElementRef,

private formatcurrencypipe:MycurrencyPipe

) {

this.el = this.elementRef.nativeElement;

}

ngOnInit(){

this.el.value = this.formatcurrencypipe.transform(this.el.value);

}

@HostListener("focus",["$event.target.value","$event"])

onFocus(value,event) {

this.el.value = this.formatcurrencypipe.parse(value); // opossite of transform

if(event.which== 9)

{

return false;

}

this.el.select();

}

@HostListener("blur", ["$event.target.value"])

onBlur(value) {

this.el.value = this.formatcurrencypipe.transform(value);

}

@HostListener('keydown', ['$event']) onKeyDown(event) {

let e = <KeyboardEvent> event;

if ([46, 8, 9, 27, 13, 110, 190].indexOf(e.keyCode) !== -1 ||

// Allow: Ctrl+A

(e.keyCode === 65 && (e.ctrlKey || e.metaKey)) ||

// Allow: Ctrl+C

(e.keyCode === 67 && (e.ctrlKey || e.metaKey)) ||

// Allow: Ctrl+V

(e.keyCode === 86 && (e.ctrlKey || e.metaKey)) ||

// Allow: Ctrl+X

(e.keyCode === 88 && (e.ctrlKey || e.metaKey)) ||

// Allow: home, end, left, right

(e.keyCode >= 35 && e.keyCode <= 39)) {

// let it happen, don't do anything

return;

}

// Ensure that it is a number and stop the keypress

if ((e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) && (e.keyCode < 96 || e.keyCode > 105)) {

e.preventDefault();

}

To use it on the component, please import the pipe first on your component.ts file as shown below

Then open component.html, add appmycurrency as an attribute on the textbox element you want to provide the currency filter

For live demo app

To change the Indonesian format to $ or your country currency change from the mycurrency.pipe.ts in the constructor class

constructor(){
    this.prefix='$'; // change this line with your country
    this.suffix='';
    this.decimal_separator='.';
    this.thousands_separator = ',';
  }

constructor(){

this.prefix='$'; // change this line with your country

this.suffix='';

this.decimal_separator='.';

this.thousands_separator = ',';

}

Read another article: How to Create Autofocus Directive Certain Elements Angular 4

Thus my article about create angular directive to format currency, hope useful.

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Sigit Prasetya Nugroho

This site is a personal Blog of Sigit Prasetya Nugroho, a Desktop developer and freelance web developer working in PHP, MySQL, WordPress.

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7 Comments

Add your comment

Dan November 2, 2017 at 2:55 pm

Sigit, the directive doesn’t seem to work if there is a default value in the input text element. By adding [(ngModel)]=”someValue”. If someValue is set in the constructor as this.someValue = 55.8. The expected result should be Rp. 55.80. Is there a way to fix this?

Sigit Prasetya Nugroho November 6, 2017 at 2:46 am
i will fix it ASAP
Thanks you 🙂
- Ashritha desireddy November 28, 2018 at 8:14 am
  I am trying to apply my directive on two binded value using [(ngModel)] and i do not want the value to get carry forwarded to backend. Is there a way to do so while applying this custom directive?

Sigit Prasetya Nugroho November 8, 2017 at 8:41 am

hello Dan, after i check, i try it using formgroup its running well.

Sigit Prasetya Nugroho November 24, 2017 at 4:05 am

Update:
add # decorator below in app.component.html at your input box

 <input type="text" #inputbox>

1	<input type="text" #inputbox>

Add this code below in yout app.component.ts

........
export class AppComponent implements OnInit {
 @ViewChild('inputbox') focus1:ElementRef;
constructor(
    private cpipe : MycurrencyPipe){}
// to invoke pipe directive to your currency format textbox use the following code
.................
 this.focus1.nativeElement.value = this.cpipe.transform(this.focus1.nativeElement.value);
...................

........

export class AppComponent implements OnInit {

@ViewChild('inputbox') focus1:ElementRef;

private cpipe : MycurrencyPipe){}

// to invoke pipe directive to your currency format textbox use the following code

.................

this.focus1.nativeElement.value = this.cpipe.transform(this.focus1.nativeElement.value);

...................

Hope fix your problem 🙂

Roshan May 5, 2018 at 2:58 am
Hi Sigit,
I followed all your steps getting the below error.. can you please let me know how to fix this error?
ERROR Error: StaticInjectorError(AppModule)[MycurrencyDirective -> MycurrencyPipe]:
StaticInjectorError(Platform: core)[MycurrencyDirective -> MycurrencyPipe]:
NullInjectorError: No provider for MycurrencyPipe!
- Sigit Prasetya Nugroho May 5, 2018 at 4:24 am
  at your component
```
@Component({
  selector: ....,
  templateUrl: ....,
  styleUrls: ....,
  providers: [MycurrencyPipe]
})

hope fix your problem
```

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