check_collections_size.js

bytesToSize = function(bytes, precision) {	
	var kilobyte = 1024;
	var megabyte = kilobyte * 1024;
	var gigabyte = megabyte * 1024;
	var terabyte = gigabyte * 1024;
	
	if ((bytes >= 0) && (bytes < kilobyte)) {
		return bytes + ' B';

	} else if ((bytes >= kilobyte) && (bytes < megabyte)) {
		return (bytes / kilobyte).toFixed(precision) + ' KB';

	} else if ((bytes >= megabyte) && (bytes < gigabyte)) {
		return (bytes / megabyte).toFixed(precision) + ' MB';

	} else if ((bytes >= gigabyte) && (bytes < terabyte)) {
		return (bytes / gigabyte).toFixed(precision) + ' GB';

	} else if (bytes >= terabyte) {
		return (bytes / terabyte).toFixed(precision) + ' TB';

	} else {
		return bytes + ' B';
	}
}



var report = [];

for(dbName in db.getMongo().getDBNames()){

	 var name = db.getMongo().getDBNames()[dbName];
	 var newDB = db.getSisterDB(name);
	
	var db_json = {'name' : name, collections : [] };

	for(dbCollName in newDB.getCollectionNames()){
			var collName = newDB.getCollectionNames()[dbCollName];
			var newColl = newDB.getCollection(collName);
			db_json.collections.push({"name":collName, "storageSize": bytesToSize(newColl.stats().storageSize,2),  "size":bytesToSize(newColl.stats().size,2), "count":newColl.stats().count} )
	}

	report.push(db_json);

}
printjson(report);