FTKhanFT

var duplicates = [];
db.getCollection('CollectionName').aggregate([   	// CollectionName = Your collection name
  { $match: { 
    name: { "$ne": '' }  // discard selection criteria
  }},
  { $group: { 
    _id: { FieldName: "$FieldName"}, // FieldName = Matching field; can be grouped on multiple properties 
    dups: { "$addToSet": "$_id" }, // _id
    count: { "$sum": 1 } 
  }}, 

emil2k

/*
 * Copyright (c) 2017 Emil Davtyan
 * 
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions: