Nodejs - Functions

const { MongoClient } = require('mongodb');

(async (url) => {

  const connection = await MongoClient.connect(url, {
    poolSize: 10, 
    reconnectTries: Number.MAX_VALUE, 
    reconnectInterval: 1000, 
    useNewUrlParser: true
  })
  
  let dbo = connection.db("mydb");
  
  /*
  dbo.collection("orders").insertMany([
    { "_id" : 1, "item" : "almonds", "price" : 12, "quantity" : 2 },
    { "_id" : 2, "item" : "pecans", "price" : 20, "quantity" : 1 },
  ])

  dbo.collection("inventory").insertMany([
    { "_id" : 1, "sku" : "almonds", description: "product 1", "instock" : 120 },
    { "_id" : 2, "sku" : "bread", description: "product 2", "instock" : 80 },
    { "_id" : 3, "sku" : "cashews", description: "product 3", "instock" : 60 },
    { "_id" : 4, "sku" : "pecans", description: "product 4", "instock" : 70 },
    { "_id" : 5, "sku": null, description: "Incomplete" },
  ])
  */

  dbo.collection('orders')
    .aggregate([{ $lookup: { from: "inventory", localField: "item", foreignField: "sku", as: "inventory_docs" } }])
    .toArray((err, docs) => console.log(JSON.stringify(docs)))
  
  connection.close()

})("mongodb://127.0.0.1:27017");

/*
  // ROLE INDEXI

  dbo.collection("roles").createIndex(
    { status : 1 }, 
    { 
      unique: true,
      partialFilterExpression: { status: true } 
    }
  )

*/