WMS OpenLayers click on thumbnail image to show Layer

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/openlayers/2.11/OpenLayers.js"></script>
<body onload="init()">
     <h1>Klick on the images to toggle the layer visibility</h1>
<div id="thumbnails">
    <img class="vorschau" id="wms" src="http://fs1.directupload.net/images/150615/cxsz5i2v.jpg" />
    <img class="vorschau" id="wms2" src="http://fs1.directupload.net/images/150615/ibtqm6lf.jpg" />
    </div>
    <div></div>
    <div id="map" class="smallmap"></div>

    
</body>

CSS

#map {
    width: 100%;
    height: 400px;
    border: 1px solid #dddddd;
    margin-top:10px;
}
.vorschau {
    width: 150px;
    height:80px;

    cursor:pointer;
    border: 1px solid #00008B;
}
#thumbnails
{
    
   margin-bottom: 15px;
}

JavaScript

var map;
var layer, wms;

function init() {
    map = new OpenLayers.Map('map', {
        maxExtent: new OpenLayers.Bounds(-20027593.947852, -3249680.8301405, -4373290.5572275, 12404622.560484)
    });
    wms = new OpenLayers.Layer.WMS(
        "States", "https://ahocevar.com/geoserver/wms", {
        layers: 'topp:states',
        transparent: 'true'
    }, {
        visibility: false
    });
    wms2 = new OpenLayers.Layer.WMS(
        "Tasmania", "http://demo.opengeo.org/geoserver/wms", {
        layers: 'topp:tasmania',
        transparent: 'true'
    }, {
        visibility: false,
        displayOutsideMaxExtent: true
    });

    var osm = new OpenLayers.Layer.OSM("OSM");
    map.addLayers([osm, wms, wms2]);
    var mittelpunkt = new OpenLayers.LonLat(-98.7, 39.9).transform(new OpenLayers.Projection("EPSG:4326"), new OpenLayers.Projection("EPSG:3857"));
    map.setCenter(mittelpunkt, 3);

    var tassie = new OpenLayers.LonLat(146.6, -42).transform(new OpenLayers.Projection("EPSG:4326"), new OpenLayers.Projection("EPSG:3857"));

    map.addControl(new OpenLayers.Control.LayerSwitcher());



    $(".vorschau").on("click", function () {
        switchlayer = eval(this.id);
        if (switchlayer.visibility === false) {
            switchlayer.setVisibility(true);
        } else {
            switchlayer.setVisibility(false);
        }

        if (this.id === 'wms2') {

            map.setCenter(tassie, 6);
        } else {
            map.setCenter(mittelpunkt, 3);
        }
    });


}