Add size() with tests and docs.

README.md

@@ -157,6 +157,9 @@ Removes the edge that runs from vertex `u` to vertex `v`.  If the graph is undir
 #### `graph.removeEdges(edgePairsOrLabel)`
 Removes a collection of edges from the graph.  If `edgePairsOrLabel` is an array of edge-pairs (each edge-pair an array of two vertex ids), those edges will be removed.  If `edgePairsOrLabel` is a label, all edges with that label will be removed.
 
+#### `graph.size()`
+Returns the number of edges in the graph.
+
 #### `graph.equals(anotherGraph, [matchWeights])`
 Returns `true` when `anotherGraph` has the same graph structure and vertex ids, and returns `false` otherwise.  This ignores all labels and vertex data, but takes into account if the graphs are directed or not.  When `matchWeights` is `true`, it will require that edge weights also correspond for the two graphs to be considered equal.
 

lib/graph.js

@@ -19,6 +19,7 @@ exports = module.exports = internals.Graph = function (definition) {
     this._vertexLabels = {};
     this._edges = {};
     this._edgeLabels = {};
+    this._size = 0;
 
     var vertexDefn;
     var vid;
@@ -275,6 +276,8 @@ internals.Graph.prototype.addEdge = function (u, v, info) {
         this._setEdge(v, u, info);
     }
 
+    this._size++;
+
     return this;
 };
 
@@ -321,6 +324,8 @@ internals.Graph.prototype.removeEdge = function (u, v) {
         this._unsetEdge(v, u);
     }
 
+    this._size--;
+
     return this;
 };
 
@@ -337,6 +342,11 @@ internals.Graph.prototype.removeEdges = function (pairs /* or a label */) {
     return this;
 };
 
+internals.Graph.prototype.size = function () {
+
+    return this._size;
+};
+
 internals.Graph.prototype.equals = function (graph, matchWeights) {
 
     if (this.directed !== graph.directed) {

test/index.js

@@ -1638,6 +1638,43 @@ describe('Gert', function () {
             done();
         });
 
+        it('size() returns the size of a graph or digraph.', function (done) {
+
+            var digraph = new Graph({
+                directed: true,
+                edges: [
+                    ['a', 'b'],
+                    ['b', 'a'],
+                    ['b', 'c'],
+                    ['b', 'b']
+                ]
+            });
+
+            digraph.addEdge('c', 'a');
+            digraph.addEdge('c', 'b');
+            digraph.removeEdge('a', 'b');
+            digraph.updateEdge('c', 'a', {});
+
+            var nondigraph = new Graph({
+                directed: false,
+                edges: [
+                    ['a', 'b'],
+                    ['b', 'c'],
+                    ['b', 'b']
+                ]
+            });
+
+            nondigraph.removeEdge('a', 'b');
+            nondigraph.removeEdge('b', 'c');
+            nondigraph.addEdge('c', 'a');
+            nondigraph.updateEdge('b', 'b', {});
+
+            expect(digraph.size()).to.equal(5);
+            expect(nondigraph.size()).to.equal(2);
+
+            done();
+        });
+
         it('equals(graph) says digraphs and non-digraphs are not equal.', function (done) {
 
             var graph = new Graph({ directed: false });