how do i loop through xm document using javascript?

this is my xml output which i want to excess through java script, i want to excess the attributes of <marker /> i.e NewsID1 seperatly for each <markers></markers> tags

<markerMain>
    <markers>
      <marker NewsID1="9" />
      <marker NewsID1="10" />
    </markers>
    <markers>
        <marker NewsID1="10"/>
    </markers>
</markerMain>`

i am using this code for now

 var xml = data.responseXML;
    var markerMain = xml.documentElement.getElementsByTagName("markerMain");
    //var markers = xml.documentElement.getElementsByTagName("markers");



    for (var j = 0; j < markerMain.length; j++) 
    {
        var markers         = markerMain[j];

        var html ='';
        for (var i = 0; i < markers.length; i++) 
        {
            var NewsID1         = markers[i].getAttribute("NewsID1");
        }
     }

but its not working