label-to-placeholder.js

$('form :input').each(function(index, elem) {

    var eId = $(elem).attr('id');

    var label = null;

    if (eId && (label = $(elem).parents('form').find('label[for='+eId+']')).length === 1) {

        $(elem).attr('placeholder', $(label).html());

        $(label).addClass('hide-label');

    }
  
 });

Great snippet. I like that it only hides the labels!

Works great, but is also pulls in any HTML markup that is in the comment as well.

For example, it pulled in my < span > tag from my required fields.