Extract single value from geoServer getfeatureinfo

I am trying extract a single value using getfeatureinfo. i have used the exact code given by GeoServer.

                map.events.register('click', map, function (e) {
                document.getElementById('nodelist').innerHTML = "Loading... please wait...";
                var params = {
                    REQUEST: "GetFeatureInfo",
                    EXCEPTIONS: "application/vnd.ogc.se_xml",
                    BBOX: map.getExtent().toBBOX(),
                    SERVICE: "WMS",
                    INFO_FORMAT: 'text/html',
                    QUERY_LAYERS: map.layers[0].params.LAYERS,
                    FEATURE_COUNT: 50,
                    Layers: 'Wind Speed',
                    WIDTH: map.size.w,
                    HEIGHT: map.size.h,
                    format: format,
                    s tyles: map.layers[0].params.STYLES,
                        srs: map.layers[0].params.SRS};

                    // handle the wms 1.3 vs wms 1.1 madness
                if(map.layers[0].params.VERSION == "1.3.0") {
                    params.version = "1.3.0";
                    params.j = parseInt(e.xy.x);
                    params.i = parseInt(e.xy.y);
                } else {
                    params.version = "1.1.1";
                    params.x = parseInt(e.xy.x);
                    params.y = parseInt(e.xy.y);
                }

                // merge filters
                if(map.layers[0].params.CQL_FILTER != null) {
                    params.cql_filter = map.layers[0].params.CQL_FILTER;
                } 
                if(map.layers[0].params.FILTER != null) {
                    params.filter = map.layers[0].params.FILTER;
                }
                if(map.layers[0].params.FEATUREID) {
                    params.featureid = map.layers[0].params.FEATUREID;

                }

               OpenLayers.loadURL("http://localhost:8080/geoserver/GIS/wms", params, this, setHTML, setHTML);

                OpenLayers.Event.stop(e);
            });

        }

        // sets the HTML provided into the nodelist element
        function setHTML(response){

            document.getElementById('nodelist').innerHTML = response.responseText;

        };

Now I want to retrieve a single value from response. I tried parsing. Changing COntent.ftl. But Still the code returned is in HTML Format. When I try to use response.responseXML it returns Null. It would be helpful if anybody could provide any input. Its frustating as it gives the feeling it is straightforward but still I am on it since last three days.

Thanks, Astha

You can try to parse the data as JSON first in your setHTML function and then look for the attribute you need.

var data = JSON.parse(response.responseText);