Like this?
function showOneLayer(["ESP Scan", "SP Scan", "BT Scan", "GTC Scan"], "Cadent Trace"); {
var docOCGs = this.getOCGs();
for (var x=0; x < docOCGs.length; x++) {
var layer = docOCGs[x];
if (allLayers.indexOf(layer.name)!=-1) {
layer.state = (layerName==layerToShow);
}
}
}