Why Undefined?

Question

MongoDB

let Categories
mongoClient.connect((error, client) => {
  if(error) throw error

  let db = client.db('Project')
  let categories = db.collection('categories')


  categories.find().toArray((error, results) => {
            
        Categories = results
        console.log(Categories) // Все ок, выводит
        client.close()
  })
})

console.log(Categories) // undefined

How to get data from collection?

Answer 1

The idea is undefined, because you read to the console synchronously, and the variable in the callback is written asynchronously.