Angular2 - Input Field To Accept Only Numbers

Question

In Angular2, how can I mask an input field(textbox) such that it accepts only numbers and not alphabets?

I have the following HTML input:

<input type="text" *ngSwitchDefault class="form-control" (change)="onInputChange()" [(ngModel)]="config.Value" focus)="handleFocus($event)" (blur)="handleBlur($event)"/>

The above input is a generic text input which may either be used as a simple text field or as a numeric field, (for example to show the Year).

Using angular2, how can I use the same input control and apply some sort of filter/mask on this field, such that it accepts only numbers? What are the different ways I can achieve this?

Note: I need to achieve this using only textbox and not using input number type.

Answer 1

Just Create a directive and add below hostlistener:

@HostListener('input', ['$event'])
    onInput(event: Event) {
        this.elementRef.nativeElement.value = (<HTMLInputElement>event.currentTarget).value.replace(/[^0-9]/g, '');
    }

Replace invalid text with empty. All keys and key combinations will now work across all browsers till IE9.

Answer 2

I have made some modifications in the above directive and implemented min, max, maxlength.

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

@Directive({
  selector: '[numberOnly]'
})
export class NumbersOnlyDirective {

  private regex: RegExp = new RegExp(/[0-9]/g);
  // Allow key codes for special events. Reflect :
  private specialKeys: Array<number> = [46, 8, 9, 27, 13, 110, 190, 35, 36, 37, 39];
  // Backspace, tab, end, home

  @Input() maxlength: number;
  @Input() min: number;
  @Input() max: number;

  constructor(private el: ElementRef) {
  }
    @HostListener('keydown', ['$event'])
    onKeyDown(event: KeyboardEvent) {
    e = <KeyboardEvent>event;

if ((
  (this.specialKeys.indexOf(event.which) > -1) ||
  // to allow backspace, enter, escape, arrows  
  (e.which == 65 && e.ctrlKey == true) ||
  // Allow: Ctrl+C        
  (e.which == 67 && e.ctrlKey == true) ||
  // Allow: Ctrl+X
  (e.which == 88 && e.ctrlKey == true))) {
  return;
} else if (// to allow numbers  
  (e.which >= 48 && e.which <= 57) ||
  // to allow numpad number  
  (event.which >= 96 && event.which <= 105)) { }
else {
      event.preventDefault();
    }
    let current: string = this.el.nativeElement.value;

    let next: string = current.concat(event.key);
    if ((next && !String(next).match(this.regex)) ||
      (this.maxlength && next.length > this.maxlength) ||
      (this.min && +next < this.min) ||
      (this.max && +next >= this.max)) {
      event.preventDefault();
    }

  }
}

Answer 3

You can use angular2 directives. Plunkr

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

@Directive({
  selector: '[OnlyNumber]'
})
export class OnlyNumber {

  constructor(private el: ElementRef) { }

  @Input() OnlyNumber: boolean;

  @HostListener('keydown', ['$event']) onKeyDown(event) {
    let e = <KeyboardEvent> event;
    if (this.OnlyNumber) {
      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();
        }
      }
  }
}

and you need to write the directive name in your input as an attribute

<input OnlyNumber="true" />

don't forget to write your directive in declarations array of your module.

By using regex you would still need functional keys

export class OnlyNumber {

  regexStr = '^[0-9]*$';
  constructor(private el: ElementRef) { }

  @Input() OnlyNumber: boolean;

  @HostListener('keydown', ['$event']) onKeyDown(event) {
    let e = <KeyboardEvent> event;
    if (this.OnlyNumber) {
        if ([46, 8, 9, 27, 13, 110, 190].indexOf(e.keyCode) !== -1 ||
        // Allow: Ctrl+A
        (e.keyCode == 65 && e.ctrlKey === true) ||
        // Allow: Ctrl+C
        (e.keyCode == 67 && e.ctrlKey === true) ||
        // Allow: Ctrl+V
        (e.keyCode == 86 && e.ctrlKey === true) ||
        // Allow: Ctrl+X
        (e.keyCode == 88 && e.ctrlKey === true) ||
        // Allow: home, end, left, right
        (e.keyCode >= 35 && e.keyCode <= 39)) {
          // let it happen, don't do anything
          return;
        }
      let ch = String.fromCharCode(e.keyCode);
      let regEx =  new RegExp(this.regexStr);    
      if(regEx.test(ch))
        return;
      else
         e.preventDefault();
      }
  }
}

Answer 4

In order to accomplish this, I bound a function to the onInput method like this:

(input)="stripText(infoForm.get('uin'))

Here is the example inside my form:

<form [formGroup]="infoForm" (submit)="next()" class="ui form">
    <input type="text" formControlName="uin" name="uin" id="uin" (input)="stripText(infoForm.get('uin'))" required/>
</form>

Then I added the following function to my component:

  stripText(control: FormControl) {
   control.setValue(control.value.replace(/[^0-9]/g, ''));
  }

This regex /[^0-9]/g searches for anything that is not a number and using .replace I set it to be replaced by nothing. So when a user tries to type in a character that is not a number (in this case a character that is not zero through nine), it appears as if nothing happens in the text box.

Answer 5

Here is easy one: Simple directive On keydown event it checks the length of a key is one and key is not a number to preventDefault() and it won't renders that char.

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

@Directive({
    selector: '[numbersOnly]'
})
export class NumbersOnlyDirective {
    @HostListener('keydown', ['$event'])
    keyDownEvent(event: KeyboardEvent) {
        if (event.key.length === 1 && (event.which < 48 || event.which > 57)) {
            event.preventDefault();
        }
    }

}

HTML:

<input type="text" [(ngModel)]="numModel" numbersOnly />

Limitations: It will allow pasting using a mouse that way will accept other char. To avoid that you can pass the model as input to the directive and ngOnChage to that model change value to only numbers:

Like below:

EDIT: Added Code to detect change in Model and update the input's value

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

@Directive({
    selector: '[numbersOnly]'
})
export class NumbersOnlyDirective implements OnChanges {

    @Input() numbersOnly: any;

    constructor(private el: ElementRef) {}

    @HostListener('keydown', ['$event'])
    keyDownEvent(event: KeyboardEvent) {
        // Add other conditions if need to allow ctr+c || ctr+v
        if (event.key.length === 1 && (event.which < 48 || event.which > 57)) {
            event.preventDefault();
        }
    }

    ngOnChanges(changes) {
        if (changes.numbersOnly) {
            this.el.nativeElement.value = this.el.nativeElement.value.replace(/[^0-9]/g, '');
        }
    }

}

HTML:

<input type="text" [(ngModel)]="numModel" [numbersOnly]="numModel" />

Answer 6

Use directive to restrict the user to enter only numbers in the following way:

.directive('onlyNumber', function () {
    var regExp = /^[0-9]*$/;
    return {
        require: '?ngModel',
        restrict: 'A',
        priority: 1,
        link: function (scope, elm, attrs, ctrl) {
            ctrl.$validators.onlyNumber= function (modalValue) {
                return ctrl.$isEmpty(modalValue) || regExp.test(modalValue);
            };
        }
    };
    })

In HTML:

<input id="txtRollNumber" type="text" name="rollNumber" placeholder="Enter roll number*" ng-model="rollNumber" class="form-control" maxlength="100" required only-number />

Angular2:

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

@Directive({
  selector: '[OnlyNumber]'
})
export class OnlyNumber {

  constructor(private el: ElementRef) { }

  @Input() OnlyNumber: boolean;

  @HostListener('keydown', ['$event']) onKeyDown(event) {
    let e = <KeyboardEvent> event;
    if (this.OnlyNumber) {
      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();
        }
      }
  }
}

And need to write the directive name in your input as an attribute.

<input OnlyNumber="true" />