<div id="mydiv">
 <span id='span1'>
 <span id='span2'>
</div>

$("#mydiv").find("span");

var array = jQuery.makeArray($("#mydiv").find("span"));

$("#mydiv").find("span").each(function(){}); //but i cannot really get the id and assign it to an array that is not with in the scope?(or can I)

var IDs = [];
$("#mydiv").find("span").each(function(){ IDs.push(this.id); });

var IDs = $("#mydiv span[id]")         // find spans with ID attribute
  .map(function() { return this.id; }) // convert to set of IDs
  .get(); // convert to instance of Array (optional)

var idarray = $("#myDiv")
             .find("span") //Find the spans
             .map(function() { return this.id; }) //Project Ids
             .get(); //ToArray

var arr = $.map($("#mydiv [id]"), function(n, i) {
  return n.id;
});

var arr = $.map($("#mydiv span"), function(n, i) {

var arr = $.map($("#mydiv span[id]"), function(n, i) {

var arr = $("#mydiv [id]").map(function() {
  return this.id;
});

jQuery.fn.getIdArray = function() {
  var ret = [];
  $('[id]', this).each(function() {
    ret.push(this.id);
  });
  return ret;
};

var array = $("#mydiv").getIdArray();

$(function() {

       var oArr = {};
       $("*[id]").each(function() {
           var id = $(this).attr('id');
           if (!oArr[id]) oArr[id] = true;
       });

       for (var prop in oArr)
           alert(prop);

   });