unweighted_undirected.js

class Graph {
  constructor() {
    this.numberOfVertices = 0;
    this.adjacentList = {};
  }

  addVertex(vertex) {
    if (!this.adjacentList[vertex]) {
      this.adjacentList[vertex] = [];
      this.numberOfVertices++;
      return true;
    }
    return false;
  }

  addEdge(firstVertex, secondVertex) {
    if (this.adjacentList[firstVertex] && this.adjacentList[secondVertex]) {
      this.adjacentList[firstVertex].push(secondVertex);
      this.adjacentList[secondVertex].push(firstVertex);
      return true;
    }
    return false;
  }

  removeEdge(firstVertex, secondVertex) {
    if (this.adjacentList[firstVertex] && this.adjacentList[secondVertex]) {
      this.adjacentList[firstVertex] = this.adjacentList[firstVertex].filter(
        (v) => v - secondVertex
      );
      this.adjacentList[secondVertex] = this.adjacentList[secondVertex].filter(
        (v) => v - firstVertex
      );
      return true;
    }
    return false;
  }

  removeVertex(vertex) {
    if (!this.adjacentList[vertex]) return undefined;
    while (this.adjacentList[vertex].length) {
      let temp = this.adjacentList[vertex].pop();
      this.removeEdge(vertex, temp);
    }
    delete this.adjacentList[vertex];
    this.numberOfVertices--;
    return this;
  }

  showConnections() {
    const allVertices = Object.keys(this.adjacentList);
    for (let vertex of allVertices) {
      const vertexConnections = this.adjacentList[vertex];
      let connections = "";
      for (let vertex of vertexConnections) {
        connections += vertex + " ";
      }
      console.log(vertex + " --> ", connections);
    }
  }
}

const myGraph = new Graph();
console.log(myGraph.addVertex("1"));
console.log(myGraph.addVertex("2"));
console.log(myGraph.addVertex("3"));
console.log(myGraph.addVertex("4"));
console.log(myGraph.addVertex("5"));
console.log(myGraph.addVertex("6"));
console.log(myGraph);
console.log(myGraph.addEdge("1", "2"));
console.log(myGraph.addEdge("1", "3"));
console.log(myGraph.addEdge("2", "3"));
console.log(myGraph.addEdge("2", "4"));
console.log(myGraph.addEdge("3", "5"));
console.log(myGraph);
console.log(myGraph.removeEdge("3", "5"));
console.log(myGraph.removeEdge("2", "4"));
console.log(myGraph);
console.log(myGraph.removeVertex("5"));
console.log(myGraph.removeVertex("4"));
console.log(myGraph);
myGraph.showConnections();