Javascript Data Structure Graph Undirected Graph

function UndirectedGraph() {
    this.edges = {};/*  w w  w.  j a  va2 s. c  o  m*/
}
UndirectedGraph.prototype.addVertex = function(vertex) {
    this.edges[vertex] = {};
}
UndirectedGraph.prototype.addEdge = function(vertex1, vertex2, weight) {
    if (weight == undefined) {
        weight = 0;
    }
    this.edges[vertex1][vertex2] = weight;
    this.edges[vertex2][vertex1] = weight;
}


UndirectedGraph.prototype.removeEdge = function(vertex1, vertex2) {
    if (this.edges[vertex1] && this.edges[vertex1][vertex2] != undefined) {
        delete this.edges[vertex1][vertex2];
    }
    if (this.edges[vertex2] && this.edges[vertex2][vertex1] != undefined) {
        delete this.edges[vertex2][vertex1];
    }
}


UndirectedGraph.prototype.removeVertex = function(vertex) {
    for (var adjacentVertex in this.edges[vertex]) {
        this.removeEdge(adjacentVertex, vertex);
    }
    delete this.edges[vertex];
}
var graph1 = new UndirectedGraph();
graph1.addVertex(1);
graph1.addVertex(2);
graph1.addEdge(1, 2, 1);
graph1.edges; // 1: {2: 0},  2: {1: 0}
graph1.addVertex(3);
graph1.addVertex(4);
graph1.addVertex(5);
graph1.addEdge(2, 3, 8);
graph1.addEdge(3, 4, 10);
graph1.addEdge(4, 5, 100);
graph1.addEdge(1, 5, 88);
console.log(graph1);

var graph2 = new UndirectedGraph();
graph2.addVertex(1);
graph2.addVertex(2);
graph2.addEdge(1, 2, 1);
graph2.edges; // 1: {2: 0},  2: {1: 0}
graph2.addVertex(3);
graph2.addVertex(4);
graph2.addVertex(5);
graph2.addEdge(2, 3, 8);
graph2.addEdge(3, 4, 10);
graph2.addEdge(4, 5, 100);
graph2.addEdge(1, 5, 88);
graph2.removeVertex(5);
graph2.removeVertex(1);
graph2.removeEdge(2, 3);
console.log(graph2);