Итак, для полноты, вот пример того, как получить список / массив слоев:
var formatter = new OpenLayers.Format.WMSCapabilities();
var endpoint = "path/to/wms/endpoint";
var layers = [];
// async call to geoserver (I'm using angular)
$http.get(endpoint + 'request=GetCapabilities').
success(function(data, status, headers, config) {
// use the tool to parse the data
var response = (formatter.read(data));
// this object contains all the GetCapabilities data
var capability = response.capability;
// I want a list of names to use in my queries
for(var i = 0; i < capability.layers.length; i ++){
layers.push(capability.layers[i].name);
}
}).
error(function(data, status, headers, config) {
alert("terrible error logging..");
});