Add hasEdge method

README.md

@@ -126,6 +126,10 @@ The last argument *weight* (optional) specifies the weight of this edge.
 
 Removes the edge from node *u* to node *v*. Returns *graph* to support method chaining. The arguments *u* and *v* are string identifiers for nodes. This function does not remove the nodes *u* and *v*. Does nothing if the edge does not exist.
 
+<a name="has-edge" href="#has-edge">#</a> <i>graph</i>.<b>hasEdge</b>(<i>u</i>, <i>v</i>)
+
+Returns `true` if there exists an edge from node *u* to node *v*. Returns `false` otherwise.
+
 ### Working with Edge Weights
 
 <a name="set-edge-weight" href="#set-edge-weight">#</a> <i>graph</i>.<b>setEdgeWeight</b>(<i>u</i>, <i>v</i>, <i>weight</i>)

index.d.ts

@@ -17,6 +17,7 @@ declare function Graph(serialized?: Serialized): {
     adjacent: (node: NodeId) => NodeId[];
     addEdge: (u: NodeId, v: NodeId, weight?: number | undefined) => any;
     removeEdge: (u: NodeId, v: NodeId) => any;
+    hasEdge: (u: NodeId, v: NodeId) => boolean;
     setEdgeWeight: (u: NodeId, v: NodeId, weight: EdgeWeight) => any;
     getEdgeWeight: (u: NodeId, v: NodeId) => EdgeWeight;
     indegree: (node: NodeId) => number;

index.js

@@ -33,6 +33,7 @@ function Graph(serialized) {
         adjacent: adjacent,
         addEdge: addEdge,
         removeEdge: removeEdge,
+        hasEdge: hasEdge,
         setEdgeWeight: setEdgeWeight,
         getEdgeWeight: getEdgeWeight,
         indegree: indegree,
@@ -134,6 +135,18 @@ function Graph(serialized) {
         }
         return graph;
     }
+    // Returns true if there is an edge from node u to node v.
+    function hasEdge(u, v) {
+        var has = false;
+        if (edges[u]) {
+            adjacent(u).forEach(function (_v) {
+                if (_v === v) {
+                    has = true;
+                }
+            });
+        }
+        return has;
+    }
     // Computes the indegree for the given node.
     // Not very efficient, costs O(E) where E = number of edges.
     function indegree(node) {

index.ts

@@ -24,6 +24,7 @@ function Graph(serialized?: Serialized) {
         adjacent,
         addEdge,
         removeEdge,
+        hasEdge,
         setEdgeWeight,
         getEdgeWeight,
         indegree,
@@ -143,6 +144,19 @@ function Graph(serialized?: Serialized) {
         return graph;
     }
 
+    // Returns true if there is an edge from node u to node v.
+    function hasEdge(u: NodeId, v: NodeId) {
+        let has = false;
+        if (edges[u]) {
+            adjacent(u).forEach(function(_v) {
+                if(_v === v){
+                    has = true;
+                }
+            });
+        }
+        return has;
+    }
+
     // Computes the indegree for the given node.
     // Not very efficient, costs O(E) where E = number of edges.
     function indegree(node: NodeId) {

test.js

@@ -446,6 +446,15 @@ describe("Graph", function() {
       assert.deepEqual(graph.shortestPath("a", "c"), withWeight(["a", "b", "c"], 2));
     });
   });
+
+  describe("hadEdge", function (){
+    it("Should compute hasEdge.", function (){
+      var graph = Graph().addEdge("a", "b");
+      assert.equal(graph.hasEdge("a", "b"), true);
+      assert.equal(graph.hasEdge("b", "a"), false);
+      assert.equal(graph.hasEdge("c", "a"), false);
+    });
+  })
 });
 
 function contains(arr, item){