Bulk MongoDB edit key on all documents of collection, here: lowercase string except first letter

Bulk edit documents in mongoDB collection

  var bulk = db.postnummer.initializeOrderedBulkOp();
var counter = 0;
db.postnummer.find().forEach(function(data) {
  var updoc = {
      "$set": {}
  };
  var myKey = "kommune";
  updoc["$set"][myKey] = data.kommune[0] + data.kommune.toLowerCase().substring(1);
  // queue the update
  bulk.find({
      "_id": data._id
  }).update(updoc);
  counter++;
  // Drain and re-initialize every 1000 update statements
  if (counter % 1000 == 0) {
      bulk.execute();
      bulk = db.postnummer.initializeOrderedBulkOp();
  }
  })
  // Add the rest in the queue
if (counter % 1000 != 0) bulk.execute();