How to duplicate the records in a MongoDB collection

duplicateMongoDocuments.js

// Fill out a literal array of collections you want to duplicate the records in.
// Iterate over each collection using the forEach method on the array.
// For each collection get (find) all the records and forEach on each of them.
// Remove the _id field from each record as MongoDB will generate this for you and
//    you can't have a duplicate.
// Save the record.
// This assumes that the collection does not have any unique keys set on any of the
//    other fields.
// Run this in the MongoDB shell

[db.<collection1>, db.<collection2>].forEach(function(collection)
{
	collection.find({}).forEach(function(x) { 
	    delete x._id;
	    collection.save(x); 
	});
});