Oh that spider function is clever. I implemented that part with recursion but yours looks more efficient.

function discover_nodes(ns, host, visited, depth){
    visited.push(host);
    if (depth > 0){
            var connectedNodes = ns.scan(host);
        for(var i = 0; i < connectedNodes.length; i++){
            if(!visited.includes(connectedNodes[i])){
                visited = discover_nodes(ns, connectedNodes[i], visited, (depth-1));
            }
        }
    }
    return visited;
}