node js/mongo db: Why trying to add a document to MongoDB keeps trowing me insertOne is not a function?

Question

I'm using Node.js with the MongoDB driver and, when I try to insert an element using the insertOne function it keeps throwing this error:

TypeError: users.insertOne is not a function
    at /Users/aleg/sto/servicetools/main.js:64:9
    at Layer.handle [as handle_request] (/Users/aleg/sto/servicetools/node_modules/express/lib/router/layer.js:95:5)
    at next (/Users/aleg/sto/servicetools/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/Users/aleg/sto/servicetools/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/Users/aleg/sto/servicetools/node_modules/express/lib/router/layer.js:95:5)
    at /Users/aleg/sto/servicetools/node_modules/express/lib/router/index.js:281:22
    at Function.process_params (/Users/aleg/sto/servicetools/node_modules/express/lib/router/index.js:341:12)
    at next (/Users/aleg/sto/servicetools/node_modules/express/lib/router/index.js:275:10)
    at /Users/aleg/sto/servicetools/node_modules/body-parser/lib/read.js:130:5
    at invokeCallback (/Users/aleg/sto/servicetools/node_modules/raw-body/index.js:224:16)

main.js:

const express = require("express")
const mongo = require("mongodb").MongoClient
const app = express()
const url = "mongodb://localhost:27017"
const port = 5704
const bcrypt = require("bcrypt");
app.use(express.json())
mongo.connect(
  url,
  {
    useNewUrlParser: true,
    useUnifiedTopology: true,
  },
  (err, client) => {
    if (err) {
      console.error(err)
      console.log("! database connection failed.")
      process.exit()
      return
    }
    console.log("...loading data from database...")
    db = client.db("servicetools")
    services = db.collection("services")
    settings = db.collection("settings")
    users = db.collections("users")

    })
  }
)
app.post("/STOAdmin/UserAccounts/AddSTOUserAccount", (req, res) => {
  

  users.insertOne(
      {
        username: req.body.username,
        password: req.body.password,
        admin: req.body.admin,
        enabled: req.body.enabled
      },
      (err, result) => {
        if (err) {
          console.error(err)
          res.status(500).json({ err: err })
          return
        }
        res.status(200).json({ ok: true })
      }
      )
})
app.listen(port, () => console.log("backend ready for requests"))

The code uses Express for the API Requests and it can't insert the elements from them throwing the error.

Answer 1

I resolved the problem, I did a typo in the users declaration.