How to join multiple collections in mongodb?

Question

I'm new in mongo db, i want to join 6 collections in mongodb by node.js, which none of them have the same field,I would be pleased if anyone give me a link which explains it in a simple way, i've searched a lot but i couldn't get the best solution.

Answer 1

"none of them have the same field"
How do you want to join them if they have nothing in common? If one collection has 8 elements and the other one has 7, their combination would have 56 different elements (cartesian product). With 6 collections this number can grow really quickly... Is this what you want?
https://www.w3schools.com/nodejs/nodejs_mongodb_join.asp