undirected graph

class Graph {
  private numberOfNodes: number;
  private adjacentList: { [key: string]: string[] };

  constructor() {
    this.numberOfNodes = 0;
    this.adjacentList = {};
  }

  addVertex(node: string) {
    if (!this.adjacentList[node]) {
      this.adjacentList[node] = [];
      this.numberOfNodes++;
    }
  }

  addEdge(node1: string, node2: string) {
    //undirected Graph
    if (!this.adjacentList[node1]) {
      this.addVertex(node1);
    }

    if (!this.adjacentList[node2]) {
      this.addVertex(node2);
    }

    if (!this.adjacentList[node1].includes(node2)) {
      this.adjacentList[node1].push(node2);
    }

    if (!this.adjacentList[node2].includes(node1)) {
      this.adjacentList[node2].push(node1);
    }
  }

  showConnections() {
    const allNodes = Object.keys(this.adjacentList);
    for (let node of allNodes) {
      let nodeConnections = this.adjacentList[node].sort();
      let connections = "";
      let vertex;
      for (vertex of nodeConnections) {
        connections += vertex + " ";
      }
      console.log(node + " --> " + connections);
    }
  }
}

const myGraph = new Graph();
myGraph.addVertex('0');
myGraph.addVertex('1');
myGraph.addVertex('2');
myGraph.addVertex('3');
myGraph.addVertex('4');
myGraph.addVertex('5');
myGraph.addVertex('6');
myGraph.addEdge('3', '1');
myGraph.addEdge('3', '4');
myGraph.addEdge('4', '2');
myGraph.addEdge('4', '5');
myGraph.addEdge('1', '2');
myGraph.addEdge('1', '0');
myGraph.addEdge('0', '2');
myGraph.addEdge('6', '5');

myGraph.showConnections();
//Answer:
// 0-->1 2
// 1-->3 2 0
// 2-->4 1 0
// 3-->1 4
// 4-->3 2 5
// 5-->4 6
// 6-->5