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

I saw a lot of comments about handling copy/pasting.

To piggy back off of @omeralper answer, you can add a paste event handler to the onlyNumber directive to handle copy/pasting:

 @HostListener('paste', ['$event']) onPaste(event) {
  // Don't allow pasted text that contains non-numerics
  var pastedText = (event.originalEvent || event).clipboardData.getData('text/plain');

  if (pastedText) {
    var regEx = new RegExp('^[0-9]*$');
    if (!regEx.test(pastedText)) {
      event.preventDefault();
    }
}

This will only allow content to be copy and pasted into the textbox ONLY if it is a number. That's the simplest solution. Changing the content of the clipboard to remove non-numerics is a lot more complicated and might not be worth it.

To get pasted text from IE you can use the following:

window.clipboardData.getData('Text');

Answer 2

Use pattern attribute for input like below:

<input type="text" pattern="[0-9]+" >

Answer 3

from @omeralper 's answer. I change a little bit that won't accept period ascii (keycode 110,190). and use let ch = (e.key); to compare with regular expression when you change language (such as Thai or Japanese language) it won't accept character of those language

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) {
      // console.log(event, this.OnlyNumber);
        if ([46, 8, 9, 27, 13].indexOf(e.keyCode) !== -1) {
          return;
        }
      let ch = (e.key);
      let regEx =  new RegExp(this.regexStr);   
      if(regEx.test(ch))
        return;
      else
         e.preventDefault();
    }
  }
}

hope this help :)

Answer 4

Pattern for the Valid Mobile number pattern('^((\+91-?)|0)?[0-9]{10}$')

Pattern for accept only number from text box pattern('[0-9]*')

patter for accept only number with specific number e.g: Pincode. pattern('^[0-9]{5}$')

Answer 5

With support for sanitizing pasted content:

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

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

    DIGITS_REGEXP =  new RegExp(/\D/g);
    constructor(private el: ElementRef) { 

        // Sanatize clipboard by removing any non-numeric input after pasting
        this.el.nativeElement.onpaste = (e:any) => {
            e.preventDefault();
            let text;
            let clp = (e.originalEvent || e).clipboardData;
            if (clp === undefined || clp === null) {
                text = (<any>window).clipboardData.getData('text') || '';
                if (text !== '') {
                    text = text.replace(this.DIGITS_REGEXP, '');
                    if (window.getSelection) {
                        let newNode = document.createElement('span');
                        newNode.innerHTML = text;
                        window.getSelection().getRangeAt(0).insertNode(newNode);
                    } else {
                        (<any>window).selection.createRange().pasteHTML(text);
                    }
                }
            } else {
                text = clp.getData('text/plain') || '';
                if (text !== '') {
                    text = text.replace(this.DIGITS_REGEXP, '');
                    document.execCommand('insertText', false, text);
                }
            }
        };
    }

  @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();
      }
    }

}

Answer 6

I know this is an old question, but since this is a common funcionality, I want to share the modifications I've made:

• Custom decimal separator (point or comma)
• Support for integers only or integer and decimals
• Support for positive numbers only or positives and negatives
• Validate minus sign(-) is in the beginning
• Support to mouse pasting (with some limitation though https://caniuse.com/#feat=clipboard)
• Support for Mac command key

• Replace strings like ".33" and "33." for the correct versions: 0.33 and 33.0

  import { Directive, ElementRef, HostListener, Input } from '@angular/core';
  
  @Directive({ selector: '[NumbersOnly]' })
  export class NumbersOnly { 
  
      @Input() allowDecimals: boolean = true;
      @Input() allowSign: boolean = false;
      @Input() decimalSeparator: string = '.';
  
      previousValue: string = '';
  
      // --------------------------------------
      //  Regular expressions
      integerUnsigned: string = '^[0-9]*$';
      integerSigned: string = '^-?[0-9]+$';
      decimalUnsigned: string = '^[0-9]+(.[0-9]+)?$';
      decimalSigned: string = '^-?[0-9]+(.[0-9]+)?$';
  
      /**
       * Class constructor
       * @param hostElement
       */
      constructor(private hostElement: ElementRef) { }
  
      /**
       * Event handler for host's change event
       * @param e
       */
      @HostListener('change', ['$event']) onChange(e) {
  
              this.validateValue(this.hostElement.nativeElement.value);
  }
  
  /**
   * Event handler for host's paste event
   * @param e
   */
  @HostListener('paste', ['$event']) onPaste(e) {
  
      // get and validate data from clipboard
      let value = e.clipboardData.getData('text/plain');
      this.validateValue(value);
      e.preventDefault();
  }
  
  /**
   * Event handler for host's keydown event
   * @param event
   */
  @HostListener('keydown', ['$event']) onKeyDown(e: KeyboardEvent) {
  
      let cursorPosition: number = e.target['selectionStart'];
      let originalValue: string = e.target['value'];
      let key: string = this.getName(e);
      let controlOrCommand = (e.ctrlKey === true || e.metaKey === true);
      let signExists = originalValue.includes('-');
      let separatorExists = originalValue.includes(this.decimalSeparator);
  
      // allowed keys apart from numeric characters
      let allowedKeys = [
          'Backspace', 'ArrowLeft', 'ArrowRight', 'Escape', 'Tab'
      ];
  
      // when decimals are allowed, add
      // decimal separator to allowed codes when
      // its position is not close to the the sign (-. and .-)
      let separatorIsCloseToSign = (signExists && cursorPosition <= 1);
      if (this.allowDecimals && !separatorIsCloseToSign && !separatorExists) {
  
          if (this.decimalSeparator == '.')
              allowedKeys.push('.');
          else
              allowedKeys.push(',');
      }
  
      // when minus sign is allowed, add its
      // key to allowed key only when the
      // cursor is in the first position, and
      // first character is different from
      // decimal separator
      let firstCharacterIsSeparator = (originalValue.charAt(0) != this.decimalSeparator);
      if (this.allowSign && !signExists &&
          firstCharacterIsSeparator && cursorPosition == 0) {
  
          allowedKeys.push('-');
      }
  
      // allow some non-numeric characters
      if (allowedKeys.indexOf(key) != -1 ||
          // Allow: Ctrl+A and Command+A
          (key == 'a' && controlOrCommand) ||
          // Allow: Ctrl+C and Command+C
          (key == 'c' && controlOrCommand) ||
          // Allow: Ctrl+V and Command+V
          (key == 'v' && controlOrCommand) ||
          // Allow: Ctrl+X and Command+X
          (key == 'x' && controlOrCommand)) {
          // let it happen, don't do anything
          return;
      }
  
      // save value before keydown event
      this.previousValue = originalValue;
  
      // allow number characters only
      let isNumber = (new RegExp(this.integerUnsigned)).test(key);
      if (isNumber) return; else e.preventDefault();
  }
  
  /**
   * Test whether value is a valid number or not
   * @param value
   */
  validateValue(value: string): void {
  
      // choose the appropiate regular expression
      let regex: string;
      if (!this.allowDecimals && !this.allowSign) regex = this.integerUnsigned;
      if (!this.allowDecimals && this.allowSign) regex = this.integerSigned;
      if (this.allowDecimals && !this.allowSign) regex = this.decimalUnsigned;
      if (this.allowDecimals &&  this.allowSign) regex = this.decimalSigned;
  
      // when a numbers begins with a decimal separator,
      // fix it adding a zero in the beginning
      let firstCharacter = value.charAt(0);
      if (firstCharacter == this.decimalSeparator)
          value = 0 + value;
  
      // when a numbers ends with a decimal separator,
      // fix it adding a zero in the end
      let lastCharacter = value.charAt(value.length-1);
      if (lastCharacter == this.decimalSeparator)
          value = value + 0;
  
      // test number with regular expression, when
      // number is invalid, replace it with a zero
      let valid: boolean = (new RegExp(regex)).test(value);
      this.hostElement.nativeElement['value'] = valid ? value : 0;
  }
  
  /**
   * Get key's name
   * @param e
   */
  getName(e): string {
  
      if (e.key) {
  
          return e.key;
  
      } else {
  
          // for old browsers
          if (e.keyCode && String.fromCharCode) {
  
              switch (e.keyCode) {
                  case   8: return 'Backspace';
                  case   9: return 'Tab';
                  case  27: return 'Escape';
                  case  37: return 'ArrowLeft';
                  case  39: return 'ArrowRight';
                  case 188: return ',';
                  case 190: return '.';
                  case 109: return '-'; // minus in numbpad
                  case 173: return '-'; // minus in alphabet keyboard in firefox
                  case 189: return '-'; // minus in alphabet keyboard in chrome
                  default: return String.fromCharCode(e.keyCode);
              }
          }
      }
  }
  

Usage:

 <input NumbersOnly
        [allowDecimals]="true"
        [allowSign]="true"
        type="text">