Cleaned up return values to always be an array

lib/position/bk.js

@@ -225,12 +225,7 @@ function horizontalCompaction(g, layering, root, align, reverseSep) {
     var traversalFuncs = getNextTraversalFuncs(v);
 
     while(traversalFuncs.length) {
-      // funcsOrX is an array of function calls or the xs value for v. If it's
-      // the xs value, xs has already been set as part of the function call.
-      var funcsOrX = traversalFuncs.shift()();
-      if (funcsOrX instanceof Array) {
-        traversalFuncs = funcsOrX.concat(traversalFuncs);
-      }
+      traversalFuncs = traversalFuncs.shift()().concat(traversalFuncs);
     }
   }
 
@@ -250,7 +245,8 @@ function horizontalCompaction(g, layering, root, align, reverseSep) {
       xs[v] = _.reduce(blockG.inEdges(v), function(acc, e) {
         return Math.max(acc, xs[e.v] + blockG.edge(e));
       }, 0);
-      return xs[v];
+
+      return [];
     }]);
   }
 
@@ -275,7 +271,8 @@ function horizontalCompaction(g, layering, root, align, reverseSep) {
       if (min !== Number.POSITIVE_INFINITY && node.borderType !== borderType) {
         xs[v] = Math.max(xs[v], min);
       }
-      return xs[v];
+
+      return [];
     }]);
   }