Dijkstra's Algorithm

function dijkstra(graph, startNode, endNode) {
  // Initialize distances to all nodes as infinity and the start node as 0
  const distances = {};
  distances[startNode] = 0;
  for (let node in graph) {
    if (node !== startNode) {
      distances[node] = Infinity;
    }
  }

  // Initialize an empty set and add the start node to it
  const visited = new Set();

  // Loop until we've visited all nodes
  while (!visited.has(endNode)) {
    let currentNode = null;

    // Find the node with the shortest distance from the start node
    for (let node in graph) {
      if (!visited.has(node)) {
        if (currentNode === null || distances[node] < distances[currentNode]) {
          currentNode = node;
        }
      }
    }

    // Get the neighbors of the current node and update their distances
    const neighbors = graph[currentNode];
    for (let neighbor in neighbors) {
      const distance = neighbors[neighbor];
      const totalDistance = distances[currentNode] + distance;
      if (totalDistance < distances[neighbor]) {
        distances[neighbor] = totalDistance;
      }
    }

    // Add the current node to the visited set
    visited.add(currentNode);
  }

  // Return the shortest distance from the start node to the end node
  return distances[endNode];
}

const graph = {
  A: { B: 5, C: 2 },
  B: { D: 4 },
  C: { B: 1, D: 3 },
  D: { A: 1 },
};

A ----5---- B ----4---- D
 \         |
  2        1
   \       |
    C ----3--

const shortestDistance = dijkstra(graph, 'A', 'D');
console.log(shortestDistance); // 4