mongo stuff, aggregation framework

mongo.js

db.auth('admin', '9b2EpmkFtasdfas--wrxo-NVwZp');

const SERIAL = '3e84e930-b6af-11e8-a512-9d2b3d7cbb08';
const DESCRIPTION = 'PLC_1';
const NTAGS = 22;
const MAX_ROWS = 100;

const pipelineBefore = [
  { $match: { serial: SERIAL, description: DESCRIPTION } },
  { $group: { _id: "$date", name: { $first: "$name" }, count: { $sum: 1 }} },
];

const pipelineWrong = [ { $match: { "count": { $ne: NTAGS } } } ];
const pipelineGood = [ { $match: { "count": { $eq: NTAGS }} } ];
const pipelineAfter = [ { $sort: { _id: -1 } } ];

const allTags = db.tagData.aggregate([
  { $match: { serial: SERIAL, description: DESCRIPTION } },
  { $group: { _id: "$name", count: { $sum: 1} } },
  { $project: { _id: 0, tag: "$_id" } }
]).toArray().map((e) => e.tag).sort();
uniqTags = [ ...new Set(allTags)];


const wrongLectures = db.tagData.aggregate([...pipelineBefore, ...pipelineWrong, ...pipelineAfter]);
const goodLectures = db.tagData.aggregate([...pipelineBefore, ...pipelineGood, ...pipelineAfter]);

print(`Number of Wrong lectures length: ${wrongLectures.toArray().length}`);
print(`Number of Good lectures length: ${goodLectures.toArray().length}`);


const wrongLectures = db.tagData.aggregate([...pipelineBefore, ...pipelineWrong, ...pipelineAfter])
const wrongArray = wrongLectures.toArray().slice(0, MAX_ROWS);