Validator for IP addresses in Angular reactive forms

Hey there, I'm currently trying to implement a validator for an IP address in Angular. Strangely, even when I input an invalid IP address like 12.2.2.2..., the GUI indicates it is valid (as shown in the image). However, the console logs reveal that it is actually a pattern mismatch (indicating an incorrect pattern detection). I'm feeling puzzled as to what might be missing. It's becoming confusing now and I could really use another set of eyes to pinpoint the issue.

Just to clarify, the required aspect is functioning properly with ipaddress. My confusion lies in why it's not working on pattern validation. Please refer to the image below

https://i.sstatic.net/uyh7d.png

Here is my code example on StackBlitz

Below you can find the structure of my code:

HTML Section:

<div class="form-group row required" [ngClass]="{
  'is-invalid': ipaddress.invalid && (ipaddress.dirty || ipaddress.touched),
  'is-valid': ipaddress.valid && (ipaddress.dirty || ipaddress.touched)
}">
  <label for="ipaddress" class="col-sm-3 col-form-label">IP Address</label>
  <div class="col-sm-7">
    <input type="text" class="form-control" placeholder="IP Address"
        id="ipaddress" name="ipaddress" formControlName="ipaddress"
        ngbAutofocus required>
    <div class="form-control-feedback invalid-feedback"
        *ngIf="ipaddress.errors">
      <p *ngIf="ipaddress.errors.required">IP Address is required</p>
      <p *ngIf="ipaddress.errors.pattern">Invalid IP Address format</p>
    </div>
  </div>
</div>

TS File:

this.ipaddress = new FormControl('', {
  validators: Validators.compose([
    Validators.required,
    Validators.pattern('(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)')
  ])
});

Answer №1

It seems that the inconsistency you're experiencing is due to a mix of client-side and server-side validations in your form, which Bootstrap handles differently:

Client-side validation:

  • requires the was-validated class on the <form> tag.

Server-side validation:

  • does not require the was-validated class on the <form> tag.
  • needs the .is-valid or .is-invalid class on the input control for validation feedback.

Your IP Address input control has the required attribute, enabling native browser form validation. This means it will be treated as :invalid according to CSS pseudo-class. Bootstrap offers a specific class for handling this behavior:

.was-validated .form-control:invalid {
  border-color: <red>;
  ...

By adding the was-validated class to the <form> tag, it functions as expected.

However, when using Angular validation for pattern matching:

this.ipaddress = new FormControl('', [
  Validators.required,
  Validators.pattern("....")
]);

Browser validation won't apply, so you have to manually set .is-valid or .is-invalid. Remember, Bootstrap only supports one type of validation at a time.

To resolve this issue, consider these options:

  1. Stick with client-side validation:

HTML

<input type="ipaddress"
    class="form-control"
    formControlName="ipaddress"
    required
    pattern="^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$">

Check out Stackblitz Example

  1. Implement Bootstrap's server-side validation logic:

In order to do this:

  • You should remove the was-validated class from the form tag and ensure all current controls are touched.

For example:

this.myform.markAllAsTouched();
  • Apply the .is-valid and .is-invalid classes directly to the control itself rather than its wrapper.

HTML

<input type="ipaddress"
    class="form-control"
    formControlName="ipaddress"
    [ngClass]="{
  'is-invalid': ipaddress.invalid && (ipaddress.dirty || ipaddress.touched),
  'is-valid': ipaddress.valid && (ipaddress.dirty || ipaddress.touched)
}">

See Stackblitz Example

Answer №2

If you're working with js and ts, you have the option to utilize this code snippet:

Validators.pattern('(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)')

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