What steps can be taken to avoid special characters in ion-input fields?

Question

What steps can be taken to avoid special characters in ion-input fields?

When inputting special characters into the field used for storing the alphanumeric serial number, they are accepted. I need to prevent special characters from being entered in the input field.

<ion-input [(ngModel)]="serial_number" (ngModelChange)="validation($event)" #serialno  id="serialno"  class="cac-input"></ion-input>

  validation(event) {
    const inputElement = document.getElementById('serialno') as HTMLInputElement;
    const pattern = /^[a-zA-Z0-9]*$/;
    console.log(event)
    console.log(pattern.test(event))
    let c = event.replace(/[^a-zA-Z0-9 ]/g, '');
    inputElement.value = '';
    inputElement.value = c;
    console.log(c)
    this.serial_number = c;
  }

In the past, I used regex to remove the special characters, but even after removal, the value still shows up in the input field.

Using the (keypress) event in the browser works fine, however, it does not work on Android.

The field displays properly in the app

Console logging the ngmodel field shows the correct values

javascript angular typescript ionic-framework ionic5

Answer 1

Answer №1

A custom validator can be implemented for this particular task: it accepts a regex input to check for valid and invalid characters, replaces any unwanted characters with an empty string, and handles paste events by cleaning out invalid characters. This functionality can all be achieved using the @HostListener attribute on events like keydown and paste!

This code snippet demonstrates how to create a directive:

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

@Directive({
  selector: '[appPattern]',
})
export class PatternDirective {
  @Input() appPattern: string = '[A-Za-z0-9]';

  @HostListener('keyup', ['$event']) public onKeydown(event: any) {
    const value: string = event.target.value;
    if (!value) {
      return true;
    }
    const regExpr = new RegExp(`^(${this.appPattern})+$`);
    if (!regExpr.test(value)) {
      event.target.value = value.replace(
        new RegExp(`(${this.appPattern})|.*`, 'gm'),
        '$1'
      );
      event.preventDefault();
      return false;
    }
  }

  @HostListener('paste', ['$event']) public onPaste(event: any) {
    event.preventDefault();
    let clipboardText = event.clipboardData.getData('text');
    event.target.value = clipboardText.replace(
      new RegExp(`(${this.appPattern})|.*`, 'gm'),
      '$1'
    );
  }
  constructor(private elementRef: ElementRef) {}
}

Below is an example of how to use this directive in HTML:

<ion-input
    type="text"
    [(ngModel)]="todo.title1"
    name="title1"
    appPattern="[A-Za-z0-9]"
  ></ion-input>

Check out a live demo on StackBlitz here.

Answer 2

A custom validator can be implemented for this particular task: it accepts a regex input to check for valid and invalid characters, replaces any unwanted characters with an empty string, and handles paste events by cleaning out invalid characters. This functionality can all be achieved using the @HostListener attribute on events like keydown and paste!

This code snippet demonstrates how to create a directive:

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

@Directive({
  selector: '[appPattern]',
})
export class PatternDirective {
  @Input() appPattern: string = '[A-Za-z0-9]';

  @HostListener('keyup', ['$event']) public onKeydown(event: any) {
    const value: string = event.target.value;
    if (!value) {
      return true;
    }
    const regExpr = new RegExp(`^(${this.appPattern})+$`);
    if (!regExpr.test(value)) {
      event.target.value = value.replace(
        new RegExp(`(${this.appPattern})|.*`, 'gm'),
        '$1'
      );
      event.preventDefault();
      return false;
    }
  }

  @HostListener('paste', ['$event']) public onPaste(event: any) {
    event.preventDefault();
    let clipboardText = event.clipboardData.getData('text');
    event.target.value = clipboardText.replace(
      new RegExp(`(${this.appPattern})|.*`, 'gm'),
      '$1'
    );
  }
  constructor(private elementRef: ElementRef) {}
}

Below is an example of how to use this directive in HTML:

<ion-input
    type="text"
    [(ngModel)]="todo.title1"
    name="title1"
    appPattern="[A-Za-z0-9]"
  ></ion-input>

Check out a live demo on StackBlitz here.

Answer 3

Answer №2

For a convenient one-liner solution, Ionic offers the ability to use the supported pattern attribute on ion-input:

<ion-input type="text" pattern="^[a-zA-Z0-9]*$" ></ion-input>

Answer 4

For a convenient one-liner solution, Ionic offers the ability to use the supported pattern attribute on ion-input:

<ion-input type="text" pattern="^[a-zA-Z0-9]*$" ></ion-input>

What steps can be taken to avoid special characters in ion-input fields?

Answer №1

Answer №2

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