Allow only numerical values through an ion-input in Ionic 4, preventing the input of letters and special characters

Question

Allow only numerical values through an ion-input in Ionic 4, preventing the input of letters and special characters

I am currently developing an application in Ionic 4 that requires users to enter only integer numbers (0-9). I need to prevent any other characters such as alphabets, dots, or plus signs from being entered. However, the methods I have tried so far have not completely restricted these invalid characters.

 @HostListener('input', ['$event']) onInputChange(event) {
    this.inputElement = this._el.nativeElement.getElementsByTagName('input')[0];
    const initialValue = this.inputElement.value;
    this.inputElement.value = initialValue.replace(/[^0-9]*/g, '');
    if (initialValue !== this.inputElement.value) {
       event.stopPropagation();
    }
}

While the above method is correctly updating ngModel, it still displays invalid characters in the input field.

Another approach I attempted includes the following:

html

<ion-input type="text" placeholder="Enter number"
        [(ngModel)]="userCount" 
        name="userCount" 
        (ionInput)="countChange($event)">
 </ion-input>
 Usercount: {{userCount}}

Typescript

countChange(event) {
    event.target.value = event.target.value.replace(/[^0-9]*/g, '');
}

Although the second method accurately displays the value in HTML without invalid characters, they are still visible in the input field.

For example, if "5+" is entered in the input, the ngModel value displays "5" but the input field shows "5+". Additionally, typing "5++" and then "5" changes the input field to display "55".

I am seeking a solution that will strictly restrict users from entering anything other than integer values within the range of [0-9].

typescript ionic-framework angular7 ionic4

Answer 1

Answer №1

The keypress event is recommended for this purpose. Here is a sample code snippet TS File

  numberOnlyValidation(event: any) {
    const pattern = /[0-9.,]/;
    let inputChar = String.fromCharCode(event.charCode);

    if (!pattern.test(inputChar)) {
      // Prevent input for invalid characters
      event.preventDefault();
    }
  }

HTML File

<ion-input type="text" placeholder="Enter number"
        [(ngModel)]="userCount" 
        name="userCount" 
        (keypress)="numberOnlyValidation($event)"
 </ion-input>

This solution will help you resolve the issue.

For Ionic 5, use the following directive:

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

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

  constructor() { }

  @HostListener('keypress', ['$event'])
  onInput(event: any) {
    const pattern = /[0-9]/; // Allow only integers
    let inputChar = String.fromCharCode(event.which ? event.which : event.keyCode);

    if (!pattern.test(inputChar)) {
      // Prevent input for invalid characters
      event.preventDefault();
      return false;
    }
    return true;
  }

}

Update your HTML file as follows:

<ion-input appIntegerInput inputmode="numeric" type="number"></ion-input>

Answer 2

The keypress event is recommended for this purpose. Here is a sample code snippet TS File

  numberOnlyValidation(event: any) {
    const pattern = /[0-9.,]/;
    let inputChar = String.fromCharCode(event.charCode);

    if (!pattern.test(inputChar)) {
      // Prevent input for invalid characters
      event.preventDefault();
    }
  }

HTML File

<ion-input type="text" placeholder="Enter number"
        [(ngModel)]="userCount" 
        name="userCount" 
        (keypress)="numberOnlyValidation($event)"
 </ion-input>

This solution will help you resolve the issue.

For Ionic 5, use the following directive:

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

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

  constructor() { }

  @HostListener('keypress', ['$event'])
  onInput(event: any) {
    const pattern = /[0-9]/; // Allow only integers
    let inputChar = String.fromCharCode(event.which ? event.which : event.keyCode);

    if (!pattern.test(inputChar)) {
      // Prevent input for invalid characters
      event.preventDefault();
      return false;
    }
    return true;
  }

}

Update your HTML file as follows:

<ion-input appIntegerInput inputmode="numeric" type="number"></ion-input>

Answer 3

Answer №2

I successfully resolved my issue by removing alphabetic characters from the input using the following steps:

I began by creating a utility class with the following method:

export class StringUtil {
 
    /**
     * Removes all non-numeric characters from a string.
     * @param str string
     */
    static removeNonNumerics = (str: string) => str.replace(/\D/g, '');

}

Next, I created a directive:

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

import { StringUtil } from 'src/app/shared/utils/string.util';

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

    constructor() { }

    @HostListener('input', ['$event'])
    onInput(event: any) {
        event.target.value = StringUtil.removeNonNumerics(event.target.value);
    }

}

Then, I imported the InputIntegerDirective into my page module:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';

import { FontAwesomeModule } from '@fortawesome/angular-fontawesome';
import { IonicModule } from '@ionic/angular';

import { DeliveryTimePageRoutingModule } from './delivery-time-routing.module';

import { DirectivesModule } from 'src/app/shared/directives/directives.module';
import { UiModule } from 'src/app/shared/ui/ui.module';
import { DeliveryTimePage } from './delivery-time.page';

@NgModule({
    imports: [
        CommonModule,
        DirectivesModule,
        FontAwesomeModule,
        FormsModule,
        IonicModule,
        DeliveryTimePageRoutingModule,
        ReactiveFormsModule,
        UiModule
    ],
    declarations: [DeliveryTimePage]
})
export class DeliveryTimePageModule { }

Finally, I implemented the directive on my page:

<ion-input type="text" inputmode="numeric" formControlName="deliveryTime" maxlength="3" placeholder="Delivery Time" [required]="true" appInputInteger>
</ion-input>

This directive functioned effectively on both web browsers and mobile devices.

Answer 4

I successfully resolved my issue by removing alphabetic characters from the input using the following steps:

I began by creating a utility class with the following method:

export class StringUtil {
 
    /**
     * Removes all non-numeric characters from a string.
     * @param str string
     */
    static removeNonNumerics = (str: string) => str.replace(/\D/g, '');

}

Next, I created a directive:

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

import { StringUtil } from 'src/app/shared/utils/string.util';

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

    constructor() { }

    @HostListener('input', ['$event'])
    onInput(event: any) {
        event.target.value = StringUtil.removeNonNumerics(event.target.value);
    }

}

Then, I imported the InputIntegerDirective into my page module:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';

import { FontAwesomeModule } from '@fortawesome/angular-fontawesome';
import { IonicModule } from '@ionic/angular';

import { DeliveryTimePageRoutingModule } from './delivery-time-routing.module';

import { DirectivesModule } from 'src/app/shared/directives/directives.module';
import { UiModule } from 'src/app/shared/ui/ui.module';
import { DeliveryTimePage } from './delivery-time.page';

@NgModule({
    imports: [
        CommonModule,
        DirectivesModule,
        FontAwesomeModule,
        FormsModule,
        IonicModule,
        DeliveryTimePageRoutingModule,
        ReactiveFormsModule,
        UiModule
    ],
    declarations: [DeliveryTimePage]
})
export class DeliveryTimePageModule { }

Finally, I implemented the directive on my page:

<ion-input type="text" inputmode="numeric" formControlName="deliveryTime" maxlength="3" placeholder="Delivery Time" [required]="true" appInputInteger>
</ion-input>

This directive functioned effectively on both web browsers and mobile devices.

Answer 5

Answer №3

Implement the following changes to your code. Hopefully, this will resolve the issue

updateCount(event) {
   
   this.userCount += event.target.value.replace(/[^0-9]*/g, '');
}

<ion-input type="text" placeholder="Enter number"
         name="userCount" 
        (change)="updateCount($event)">
 </ion-input>
 Usercount: {{userCount}}

Answer 6

Implement the following changes to your code. Hopefully, this will resolve the issue

updateCount(event) {
   
   this.userCount += event.target.value.replace(/[^0-9]*/g, '');
}

<ion-input type="text" placeholder="Enter number"
         name="userCount" 
        (change)="updateCount($event)">
 </ion-input>
 Usercount: {{userCount}}

Answer 7

Answer №4

If you're looking for a straightforward fix to your issue, check out this easy solution.

Step 1: Start by developing a directive that only allows numbers and save it in a dedicated folder.

number-only.directive.ts

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

@Directive({
  selector: 'input[numbersOnly]'
})
export class NumberDirective {

  constructor(private _el: ElementRef) { }

  @HostListener('input', ['$event']) onInputChange(evt) {

    if (evt.which === 8 || evt.which === 0) {
        return true;
    }

    const regex = new RegExp("^[0-9\~]*$");
    var key = String.fromCharCode(!evt.charCode ? evt.which : evt.charCode);
    // console.log(regex.test(key))
    if (!regex.test(key)) {
        evt.preventDefault();
        return false;
    }
    return true;
  }

}

Step 2: Don't forget to import the directive in your app.module file.

import { NumberDirective } from './directive/number-only.directive';
@NgModule({
  imports: [
    CommonModule,
  ],
  declarations: [NumberDirective],
  exports: []
})
export class AppModule { }

Step 3: Implement the directive in an input field as shown below.

  <input type="text" numbersOnly placeholder="Enter Mobile/Phone Number">

Answer 8

If you're looking for a straightforward fix to your issue, check out this easy solution.

Step 1: Start by developing a directive that only allows numbers and save it in a dedicated folder.

number-only.directive.ts

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

@Directive({
  selector: 'input[numbersOnly]'
})
export class NumberDirective {

  constructor(private _el: ElementRef) { }

  @HostListener('input', ['$event']) onInputChange(evt) {

    if (evt.which === 8 || evt.which === 0) {
        return true;
    }

    const regex = new RegExp("^[0-9\~]*$");
    var key = String.fromCharCode(!evt.charCode ? evt.which : evt.charCode);
    // console.log(regex.test(key))
    if (!regex.test(key)) {
        evt.preventDefault();
        return false;
    }
    return true;
  }

}

Step 2: Don't forget to import the directive in your app.module file.

import { NumberDirective } from './directive/number-only.directive';
@NgModule({
  imports: [
    CommonModule,
  ],
  declarations: [NumberDirective],
  exports: []
})
export class AppModule { }

Step 3: Implement the directive in an input field as shown below.

  <input type="text" numbersOnly placeholder="Enter Mobile/Phone Number">

Answer 9

Answer №5

After overcoming numerous obstacles, I successfully tackled this challenge where previous methods fell short, possibly due to being outdated. My solution involved creating a specific attribute that addressed the issues at hand.

bufferValue="";
isPaste=false;
@Input() maxlength=100;
@HostListener('ionInput',[$event]) ionInput($event){
   if((this.bufferValue.length+1>=$event.target.value.length || this.isPaste) && $event.target.value.length<=this.maxlength){
    this.numberInput($event.target);
    $event.srcElement.children[0].value=$event.target.value;
}
   else{
   $event.target.value=this.bufferValue;
}
}
@HostListener('keyup',['$event']) onKeyUp($event){
  if(this.bufferValue.length+1>=$event.target.value.length && $event.target.value.length<=this.maxlength){
  this.numberInput($event.target);
  $event.srcElement.children[0].value=$event.target.value;
}
else{
  $event.target.value=this.bufferValue;
}
}
@HostListener('ionChange',['$event']) ionChange($event){
  if(this.isPaste && $event.target.value.length<=this.maxlength){
    this.numberInput($event.srcElement.children[0]);
    $event.srcElement.children[0].value=$event.target.value
    this.isPaste=true;
}
this.bufferValue=$event.target.value;
}
@HostListener('paste')paste(){
 this.isPaste=true;
}
numberInput(target){
 target.value=this.removeNonNumberValue(target.value);
 this.bufferValue=target.value;
}
removeNonNumberValue(value){
  return value.replace(/[^0-9]/g,'');
}

However, there were still challenges to address as autofill functionality was affected and iPhone users scanning alphabets resulted in unexpected behavior.

Answer 10

After overcoming numerous obstacles, I successfully tackled this challenge where previous methods fell short, possibly due to being outdated. My solution involved creating a specific attribute that addressed the issues at hand.

bufferValue="";
isPaste=false;
@Input() maxlength=100;
@HostListener('ionInput',[$event]) ionInput($event){
   if((this.bufferValue.length+1>=$event.target.value.length || this.isPaste) && $event.target.value.length<=this.maxlength){
    this.numberInput($event.target);
    $event.srcElement.children[0].value=$event.target.value;
}
   else{
   $event.target.value=this.bufferValue;
}
}
@HostListener('keyup',['$event']) onKeyUp($event){
  if(this.bufferValue.length+1>=$event.target.value.length && $event.target.value.length<=this.maxlength){
  this.numberInput($event.target);
  $event.srcElement.children[0].value=$event.target.value;
}
else{
  $event.target.value=this.bufferValue;
}
}
@HostListener('ionChange',['$event']) ionChange($event){
  if(this.isPaste && $event.target.value.length<=this.maxlength){
    this.numberInput($event.srcElement.children[0]);
    $event.srcElement.children[0].value=$event.target.value
    this.isPaste=true;
}
this.bufferValue=$event.target.value;
}
@HostListener('paste')paste(){
 this.isPaste=true;
}
numberInput(target){
 target.value=this.removeNonNumberValue(target.value);
 this.bufferValue=target.value;
}
removeNonNumberValue(value){
  return value.replace(/[^0-9]/g,'');
}

However, there were still challenges to address as autofill functionality was affected and iPhone users scanning alphabets resulted in unexpected behavior.

Allow only numerical values through an ion-input in Ionic 4, preventing the input of letters and special characters

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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