得到某字段唯一的ArrayCollection

    比如得到日期字段唯一的ArrayCollection。

<script>
    var source = 
    [
          {area:"华山市",price:3000,date:"2008-01-01"},
          {area:"深圳市",price:1000,date:"2008-01-02"},
          {area:"华山市",price:3000,date:"2008-01-01"},
          {area:"清远市",price:2200,date:"2008-09-04"},
          {area:"东莞市",price:3680,date:"2008-04-01"},
          {area:"东莞市",price:3680,date:"2008-04-01"},
          {area:"梅州市",price:3380,date:"2008-06-01"},
          {area:"珠海市",price:4101,date:"2008-01-08"},
          {area:"广州市",price:3000,date:"2008-01-01"},
          {area:"深圳市",price:1000,date:"2008-01-02"},
          {area:"华山市",price:1500,date:"2008-01-09"},
          {area:"珠海市",price:4101,date:"2008-01-08"}
      ];
    function filter(source) 
    {
	var temp = new Object();
	for (var i in source)
       {
		var o = source[i];
                
		if (!temp[o.date]) 
               {
			temp[o.date] = o;
		}
	}

	var result = [];
	for (i in temp)
       {
		result.push(temp[i]);
       }

	return result;
    }

    var result = filter(source);

    for (var i = 0; i< result.length; i++) 
    {
	document.write(result[i].date + "<br/>");
    }
</script>