const ws = new WeakSet();
let user = { name: 'Alice' };

ws.add(user);
console.log(ws.has(user)); // true

user = null; // user object can now be GC'd
// The WeakSet entry is automatically removed

const ws = new WeakSet();

// ❌ Values must be objects
ws.add(42); // TypeError: Invalid value

// ❌ No iteration methods
ws.forEach(); // Not available
for (const v of ws) {} // TypeError

// ❌ No size property
console.log(ws.size); // undefined

// ✅ Only these methods work:
ws.add(obj);
ws.has(obj);
ws.delete(obj);

// 1. Prevent double-processing
const processed = new WeakSet();

function processItem(item) {
  if (processed.has(item)) return; // already processed
  processed.add(item);
  // process the item...
}

// 2. Mark objects as visited (e.g., graph traversal)
function hasCycle(graph) {
  const visited = new WeakSet();

  function dfs(node) {
    if (visited.has(node)) return true;
    visited.add(node);

    for (const neighbor of node.neighbors) {
      if (dfs(neighbor)) return true;
    }
    return false;
  }

  return dfs(graph.root);
}

// 3. Track active instances without preventing GC
const activeInstances = new WeakSet();

class Component {
  constructor() {
    activeInstances.add(this);
  }

  destroy() {
    // Cleanup logic
    activeInstances.delete(this);
  }
}