habilitar caja de texto al seleccionar menu

[raxper]

Sin <form></form>

Código Javascript:

function detener(){if (campo.disabled){campo.disabled = false;}else {campo.disabled=true;}}
 

<select onchange="detener();">
<option>aa</option>
<option>bb</option>
<option>cc</option>
</select>
<input type="text" id="campo" value="Me duermo !!! ZZ!"/>




Con <form></form>

Código Javascript:

function detener(){if (document.forms[0].campo.disabled){document.forms[0].campo.disabled = false;}else {document.forms[0].campo.disabled=true;}}
 

<form>
<select onchange="detener();">
<option>aa</option>
<option>bb</option>
<option>cc</option>
</select>
<input type="text" id="campo" value="Full Sleep!"/></form>