implemented isLeaf

Author: jiminys

.gitignore

@@ -1,2 +1,3 @@
 /build
 /node_modules
+/.vscode

lib/graph.js

@@ -270,6 +270,16 @@ Graph.prototype.neighbors = function(v) {
   }
 };
 
+Graph.prototype.isLeaf = function (v) {
+  var neighbors;
+  if (this.isDirected()) {
+    neighbors = this.successors(v);
+  } else {
+    neighbors = this.neighbors(v);
+  }
+  return neighbors.length === 0;
+};
+
 Graph.prototype.filterNodes = function(filter) {
   var copy = new this.constructor({
     directed: this._isDirected,

test/graph-test.js

@@ -514,6 +514,21 @@ describe("Graph", function() {
     });
   });
 
+  describe("neighbors", function() {
+    it("returns undefined for a node that is not in the graph", function() {
+      expect(g.neighbors("a")).to.be.undefined;
+    });
+
+    it("returns the neighbors of a node", function() {
+      g.setEdge("a", "b");
+      g.setEdge("b", "c");
+      g.setEdge("a", "a");
+      expect(_.sortBy(g.neighbors("a"))).to.eql(["a", "b"]);
+      expect(_.sortBy(g.neighbors("b"))).to.eql(["a", "c"]);
+      expect(_.sortBy(g.neighbors("c"))).to.eql(["b"]);
+    });
+  });
+
   describe("isLeaf", function() {
     it("returns false for connected node in undirected graph", function() {
       g = new Graph({directed: false});
@@ -545,21 +560,6 @@ describe("Graph", function() {
     });
   });
 
-  describe("neighbors", function() {
-    it("returns undefined for a node that is not in the graph", function() {
-      expect(g.neighbors("a")).to.be.undefined;
-    });
-
-    it("returns the neighbors of a node", function() {
-      g.setEdge("a", "b");
-      g.setEdge("b", "c");
-      g.setEdge("a", "a");
-      expect(_.sortBy(g.neighbors("a"))).to.eql(["a", "b"]);
-      expect(_.sortBy(g.neighbors("b"))).to.eql(["a", "c"]);
-      expect(_.sortBy(g.neighbors("c"))).to.eql(["b"]);
-    });
-  });
-
   describe("edges", function() {
     it("is empty if there are no edges in the graph", function() {
       expect(g.edges()).to.eql([]);