Disable a textfield on a checkbox change

HTML

<form action="process_2.php" method="post" name="dupedit">
    <input type='text' style='width:350px' id='2671997' value='Freeformdescription' />
    <input onclick='disablefield("2671997")' type='radio' value='' checked>
    
</form>

JavaScript

function disablefield(lineid) {
    var field = document.getElementById(lineid);
    return field.disabled ? field.removeAttribute('disabled') : field.setAttribute('disabled', 'disabled');
}