class Graph { 
    constructor() { 
        this.numberOfNodes = 0;
        this.adjacencyList = {
        }; 
    } 
    addVertex(node)  { 
        if(!this.adjacencyList[node]){
            this.adjacencyList[node] =[] 
        }
        this.numberOfNodes++
    } 
    addEdge(node1, node2) { 
        this.adjacencyList[node1].push(node2)
        this.adjacencyList[node2].push(node1)
    } 
    showConnections() { 
        const allNodes = Object.keys(this.adjacencyList); 
        for (let node of allNodes) { 
            let nodeConnections = this.adjacencyList[node]; 
            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