README.md

Validation

d2l-validation-custom

The d2l-validation-custom component is used to add custom validation logic to native form elements like input, select and textarea or custom form elements created with the FormElementMixin.

Native Form Elements:

• When attached to native form elements like input, select and textarea, both the d2l-validation-custom and native form element must be within a d2l-form or d2l-form-native for the validation custom to function.

Custom Form Elements:

• When attached to custom form elements created with the FormElementMixin, the d2l-validation-custom will function even if no d2l-form or d2l-form-native is present.

Usage:

<script type="module">
  import '@brightspace-ui/core/components/validation/validation-custom.js';
</script>

<d2l-input-text id="my-text-input"></d2l-input-text>
<d2l-validation-custom for="my-text-input" failure-text="My custom error message">
</d2l-validation-custom>

<script>
  const validator = document.querySelector('d2l-validation-custom');
  validator.addEventListener('d2l-validation-custom-validate', e => {
    // Implement your custom validation logic
    const myTextInput = e.detail.forElement;
    const isValid = myTextInput.value === 'secret phrase';
    e.detail.resolve(isValid);
  });
</script>

Properties:

Property	Type	Description
for	String, required	Provide the id of the form element the validation custom should validate. Both the validation custom and its target element must be within the same shadow root.
failure-text	String, required	The failure text that is displayed when the validation custom fails validation.

Events:

• d2l-validation-custom-validate: dispatched when the form element is validated giving the validation custom an opportunity to run its validation logic
  • The form element being validated can be accessed from the detail's forElement property.
  • When validation is finished, the detail's resolve function must be called with a boolean value to indicate valid or invalid. If it is not called then validation will never complete and the component will be stuck in a validating state.

ValidationCustomMixin

If you find yourself duplicating d2l-validation-custom validation logic in many places you may want to create your own custom validator using the ValidationCustomMixin.

Usage:

import { ValidationCustomMixin } from '@brightspace-ui/core/validation/validation-custom-mixin.js';

// Use the ValidationCustomMixin
class MyValidationCustom extends ValidationCustomMixin(LitElement) {

  // Implement your custom validation logic
  async validate() {
    const myTextInput = e.detail.forElement;
    return  myTextInput.value === 'secret phrase';
  }
}
customElements.define('my-validation-custom', MyValidationCustom);

Once a component has been created using the ValidationCustomMixin, it may be used exactly like a d2l-validation-custom. However, the d2l-validation-custom-validate event isn't needed because the validation logic is included in the component itself.

Future Enhancements

Looking for an enhancement not listed here? Create a GitHub issue!