I wanted to know how to use oninvalid in the text area.
<textarea type="text" pattern=".{1,255}" id="mensagem" name="mensagem" class="form-control no-resize" rows="6" placeholder="A mensagem" required maxlength="255" autofocus
oninvalid="setCustomValidity(this.validity.patternMismatch ? 'Quantidade de caracteres excedida.' : '')"></textarea>
Well, this is not working!
Expensive,
In order for the <textarea> element to be invalid it is necessary to submit the field within a <form> element, however, in its validation only the required attribute will validate the textarea. In HTML5 the pattern attribute is not available for the <textarea> element, in this case you will have to validate the length at hand.
Example to perform validation:
<form>
<textarea required oninvalid="alert('é obrigatório');"></textarea>
<button>submit</button>
</form>Hug.