Feat/level of dependency for #27

lib/dep_graph.js

@@ -178,6 +178,41 @@ DepGraph.prototype = {
       }
     }
   },
+  /**
+   * Combines all outgoingEdges of list of nodes 
+   */
+  getNodesNextLevel: function(nodes) {
+    var source = this;
+    var nodesInLevel = []
+    for (i = 0; i < nodes.length; i++) {
+      nodesInLevel = nodesInLevel.concat(source.outgoingEdges[nodes[i]])
+    }
+    return [...new Set(nodesInLevel)]
+  },
+  /**
+   * Get nodes at each level 
+   * .e.g getNodesEachLevel() 
+   */
+  getNodesEachLevel: function(nodes, out, level) {
+    if(this.circular){
+      throw new Error("getNodesEachLevel only works for trees")
+    }
+    if(out == undefined){
+      out = []
+    }
+    if(nodes == undefined){
+      nodes = [Object.keys(this.nodes)[0]] //set root
+      out.push(nodes)
+      level = 0
+    }
+    if(this.getNodesNextLevel(nodes).length == 0){
+      return out
+    }else{
+      out.push(this.getNodesNextLevel(nodes))
+    }
+    level++
+    return this.getNodesEachLevel(out[level], out, level)
+  },
   /**
    * Return a clone of the dependency graph. If any custom data is attached
    * to the nodes, it will only be shallow copied.