Here's a revised version which uses jQuery's attributeStartsWith selector to generically find all elements with 'id' starting with "answer". Now we handle input, text area, etc.
var specialPrefix = "***";
$('[id^="answer"]').each(function() {
var value = $(this).attr('value');
if (value.lastIndexOf(specialPrefix, 0) == 0){
$(this)
.attr('value', '')
.attr('placeholder', value.substring(specialPrefix.length));
}
});