const graph = {};
graph.you = ["alice", "bob", "claire"];
graph.bob = ["anuj", "peggy"];
graph.alice = ["peggy"];
graph.claire = ["thom", "jonny"];
graph.anuj = [];
graph.peggy = [];
graph.thom = [];
graph.jonny = [];

/**
 * Determine whether a person is a seller
 * @param {string} name Friend's name
 * @returns {boolean} Result of checking
 */
const personIsSeller = name => name[name.length - 1] === "m";

/**
 * Find a mango seller
 * @param {string} name Friend's name
 * @returns {boolean} Search results
 */
const search = name => {
  let searchQueue = [...graph[name]];
  // This array is how you keep track of which people you've searched before.
  const searched = [];
  while (searchQueue.length) {
    const person = searchQueue.shift();
    // Only search this person if you haven't already searched them
    if (searched.indexOf(person) === -1) {
      if (personIsSeller(person)) {
        console.log(`${person} is a mango seller!`);
        return true;
      }
      searchQueue = searchQueue.concat(graph[person]);
      // Marks this person as searched
      searched.push(person);
    }
  }
  return false;
};

search("you"); // thom is a mango seller!