I'm new to the MEAN Stack and I'm trying to learn how it works building a stock application. In the project I first add a stock with some details (Date, user whom created the stock, etc) and then in the same page add the stock items. So I thought the best way to do it is to create a collection for stocks and a collection for items so I then can query for related items. I need to insert a reference into each of the stock items. How can I get the collection Id so then I can refer it into the item model?