Iterating over a mongodb cursor serially (waiting for callbacks before moving to next document)

A more modern approach that uses async/await:

const cursor = db.collection("foo").find({});
while(await cursor.hasNext()) {
  const doc = await cursor.next();
  // process doc here
}

Notes:

• This may be even more simple to do when async iterators arrive.
• You’ll probably want to add try/catch for error checking.
• The containing function should be async or the code should be wrapped in (async function() { ... })() since it uses await.
• If you want, add await new Promise(resolve => setTimeout(resolve, 1000)); (pause for 1 second) at the end of the while loop to show that it does process docs one after the other.