dfsAirportRoutes.js

const airports = 'ATL DXB DFW HND LHR DEN IST ORD DEL PVG LAX CAN CDG AMS SIN'.split(' ');
const routes = [
  ['ATL', 'LAX'],
  ['ATL', 'DFW'],
  ['DXB', 'ATL'],
  ['LAX', 'IST'],
  ['DEN', 'ORD'],
  ['DEN', 'PVG'],
  ['PVG', 'AMS'],
  ['DEL', 'AMS'],
  ['AMS', 'DXB'],
  ['AMS', 'LHR'],
  ['AMS', 'ATL'],
];

const adjacencyList = new Map();

function addNode(airport) {
  adjacencyList.set(airport, []);
}

function addEdge(origin, destination) {
  adjacencyList.get(origin).push(destination);
  adjacencyList.get(destination).push(origin);
}

airports.forEach(addNode);
routes.forEach(route => addEdge(...route));

console.log(adjacencyList);

function findRoute(source, destination, visited = new Set(), foundRoute = []) {
  visited.add(source);
  foundRoute.push(source);
  const destinations = adjacencyList.get(source);
  for (const dest of destinations) {
    if (dest === destination) {
      foundRoute.push(destination);
      return foundRoute;
    }
    // dfs recur
    if (!visited.has(dest) && findRoute(dest, destination, visited, foundRoute)) return foundRoute;
  }
  foundRoute.pop();
  return false;
}

// AMS -> LAX
const foundRoute = findRoute('AMS', 'LAX');

console.log(foundRoute ? `Find route: ${foundRoute.join(' -> ')}` : 'Route from AMS not found');