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 $("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).remove();
    }
 });