rimuovere attributo scrivendo in una textarea

[cavicchiandrea]

<form method="post" name="modulo">
<textarea id="risp1" name="risp1" onkeyup="myFunction()"></textarea>    
<textarea id="risp2" name="risp2" disabled></textarea>
</form>

function myFunction() {    
    
 var risp1 = document.getElementById("risp1").value;
    
if (risp1.length > 4) {


$('#risp2').removeAttr("disabled");    
    }else{
$('#risp2').attr('disabled');
}
    
}