Checking for data with JavaScript

[lattapamp]

I get data from XML. I need to check data and if data is null I must hide this.How can I check?\[code\] <script> downloadUrl("gxml.php", function(data) { var xml = data.responseXML; var markers = xml.documentElement.getElementsByTagName("marker"); for (var i = 0; i < markers.length; i++) { var oid = markers.getAttribute("objectid"); var status = markers.getAttribute("status"); var title = markers.getAttribute("title"); var volume = markers.getAttribute("volume"); var kwh = markers.getAttribute("kwh"); var puser = markers.getAttribute("puser"); var ucomp = markers.getAttribute("ucomplate"); var udate = markers.getAttribute("udate"); var suser = markers.getAttribute("suser"); var scomp = markers.getAttribute("scomplate"); var sdate = markers.getAttribute("sdate"); var type = markers.getAttribute("type"); var point = new google.maps.LatLng( parseFloat(markers.getAttribute("lat")), parseFloat(markers.getAttribute("lng"))); var html = "ObjectID:" + oid + " <br/> Title:" + title +" <br/>Status:" + status + " <br/>Volume:" + volume + " <br/> KWh:" + kwh + " <br/>User:" + puser + " <br/> User Date:" + udate + " <br/> User Complate :" + ucomp + " <br/>Super user:" + suser + " <br/> S .User Date:" + sdate + " <br/> S. User Complate :" + scomp + "<br/> <a href=http://stackoverflow.com/"edit.php\">Add/Edit</a>";</script>// this data i get from xml. i`m need to chek this null or not null\[/code\]