Depth-First Search.js

class Graph {
  constructor() {
    this.adjacencyList = {};
  }

  addVertex(vertex) {
    if (!this.adjacencyList[vertex]) {
      this.adjacencyList[vertex] = [];
    }
  }

  addEdge(vertex1, vertex2) {
    this.adjacencyList[vertex1].push(vertex2);
    this.adjacencyList[vertex2].push(vertex1);
  }

  dfsRecursive(startingVertex) {
    const result = [];
    const visited = {};

    const dfs = (vertex) => {
      if (!vertex) return;

      visited[vertex] = true;
      result.push(vertex);

      this.adjacencyList[vertex].forEach((neighbor) => {
        if (!visited[neighbor]) {
          dfs(neighbor);
        }
      });
    };

    dfs(startingVertex);
    return result;
  }
}

// Usage example:
const graph = new Graph();

graph.addVertex("A");
graph.addVertex("B");
graph.addVertex("C");
graph.addVertex("D");
graph.addEdge("A", "B");
graph.addEdge("A", "C");
graph.addEdge("B", "D");
graph.addEdge("C", "D");

console.log(graph.dfsRecursive("A")); // Output: [ 'A', 'B', 'D', 'C' ]