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BFS (graph + queue), .

Breadth-first traversal of an adjacency list using a queue.

bfs.js
const graph = {
  A: ["B", "C"],
  B: ["D", "E"],
  C: ["F"],
  D: [],
  E: ["F"],
  F: [],
};

function bfs(start) {
  const queue = [start];
  const seen = {};
  const order = [];
  while (queue.length > 0) {
    const node = queue.shift();
    if (seen[node]) continue;
    seen[node] = true;
    order.push(node);
    for (const nb of graph[node]) {
      if (!seen[nb]) queue.push(nb);
    }
  }
  return order;
}

bfs("A");

What to watch

The graph draws as a node-link diagram (current node glows); the queue fills from the back and drains from the front.

Reading bfs (graph + queue)on a page only gets you so far - code is a process, and the process happens at runtime where you can't normally see it. In NeonFlow, this exact program runs step by step: every call opens a frame, every branch picks a path, and every value moves through memory in front of you. That's the fastest way to actually understand how bfs (graph + queue) works.

Run bfs (graph + queue) yourself

Open NeonFlow, paste this code (or any of your own), and scrub through it one step at a time.

Open NeonFlow