<select id="autoplay">
    <option data-autoplay="">no</option>
    <option data-autoplay="1">yes</option>
  </select>

$("#autoplay option:selected").attr("data-autoplay");

$("#autoplay option:selected").data("autoplay");

var autopplay =  $('#autoplay option:selected').attr('data-autoplay');

if (!autoplay || autoplay == '') {
    // an empty string was returned
}
else if (autoplay == 1) {
    /* remember not to trust your users, so validate in/on the server
       if you're storing the variable/result...
    // 1 was returned
}