db collection is not a function when using MongoClient v3 0

Question

I have been trying W3schools tutorial on nodeJS with MongoDB    When I try to implement this example in a nodeJS environment and invoke the function with an AJAX call  I got the error below   TypeError  db collection is not a function     at c  Users user Desktop Web Project WebService JS 79 14     at args push  c  Users user node modules mongodb lib utils js 431 72      at c  Users user node modules mongodb lib mongo client js 254 5     at connectCallback  c  Users user node modules mongodb lib mongo client js 933 5      at c  Users user node modules mongodb lib mongo client js 794 11     at  combinedTickCallback  internal process next tick js 73 7      at process  tickCallback  internal process next tick js 104 9    Please find below my implemented code   var MongoClient   require  mongodb   MongoClient  var url    mongodb   localhost 27017 mytestingdb    MongoClient connect url  function err  db      if  err  throw err    db collection  customers   findOne     function err  result        if  err  throw err      console log result name       db close                Note that the error occurs whenever the execution hits   db collection  customers   findOne     function err  result       Also  note  in case it matters  that I have installed the latest MongoDB package for node JS  npm install mongodb   and the MongoDB version is MongoDB Enterprise 3 4 4  with MongoDB Node js driver v3 0 0-rc0

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MongoClient connect url  err  client    gt        if err  throw err       let database   client db  databaseName         database collection  name   find        toArray  err  results    gt            if err  throw err           results forEach  value   gt               console log value name                           The only problem with your code is that you are accessing the object that s holding the database handler   You must access the database directly  see database variable above    This code will return your database in an array and then it loops through it and logs the name for everyone in the database

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If someone is still trying how to resolve this error  I have done this like below   const MongoClient   require  mongodb   MongoClient     Connection URL const url    mongodb   localhost 27017      Database Name const dbName    mytestingdb    const retrieveCustomers    db  callback   gt          Get the customers collection     const collection   db collection  customers           Find some customers     collection find     toArray  err  customers    gt           if err  throw err        console log  Found the following records          console log customers        callback customers              const retrieveCustomer    db  callback   gt          Get the customers collection     const collection   db collection  customers           Find some customers     collection find   name    mahendra    toArray  err  customers    gt           if err  throw err        console log  Found the following records          console log customers        callback customers              const insertCustomers    db  callback   gt           Get the customers collection     const collection   db collection  customers        const dataArray     name    mahendra     name   divit     name    aryan             Insert some customers     collection insertMany dataArray   err  result   gt            if err  throw err          console log  Inserted 3 customers into the collection            callback result                 Use connect method to connect to the server MongoClient connect url   useUnifiedTopology  true     err  client    gt      console log  Connected successfully to server      const db   client db dbName     insertCustomers db      gt        retrieveCustomers db      gt            retrieveCustomer db      gt                client close

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It used to work with the older versions of MongoDb client   2 2 33 Option 1  So you can either use the older version npm uninstall mongodb --save  npm install mongodb 2 2 33 --save  Option 2  Keep using the newer version  3 0 and above  and modify the code a little bit  let MongoClient   require  mongodb   MongoClient  MongoClient connect  mongodb   localhost 27017   function err  client     if err  throw err    let db   client db  myTestingDb      db collection  customers   find   toArray function err  result       if err  throw err      console log result       client close

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MongoDB queries return a cursor to an array stored in memory  To access that array s result you must call  toArray   at the end of the query     db collection  customers   find     toArray

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For those that want to continue using version  3 0 1 be aware of the changes to how you use the MongoClient connect   method   The callback doesn t return db instead it returns client  against which there is a function called db dbname  that you must invoke to get the db instance you are looking for   const MongoClient   require  mongodb   MongoClient  const assert   require  assert        Connection URL const url    mongodb   localhost 27017       Database Name const dbName    myproject       Use connect method to connect to the server MongoClient connect url  function err  client      assert equal null  err     console log  Connected successfully to server       const db   client db dbName      client close

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For people on version 3 0 of the MongoDB native NodeJS driver    This is applicable to people with  mongodb     3 0 0-rc0   or a later version in package json  that want to keep using the latest version     In version 2 x of the MongoDB native NodeJS driver you would get the database object as an argument to the connect callback   MongoClient connect  mongodb   localhost 27017 mytestingdb    err  db    gt         Database returned       According to the changelog for 3 0 you now get a client object containing the database object instead   MongoClient connect  mongodb   localhost 27017    err  client    gt         Client returned   var db   client db  mytestingdb          The close   method has also been moved to the client  The code in the question can therefore be translated to   MongoClient connect  mongodb   localhost   function  err  client      if  err  throw err     var db   client db  mytestingdb       db collection  customers   findOne     function  findErr  result        if  findErr  throw findErr      console log result name       client close

User · Answer

I did a little experimenting to see if I could keep the database name as part of the url   I prefer the promise syntax but it should still work for the callback syntax   Notice below that client db   is called without passing any parameters   MongoClient connect       mongodb   localhost 27017 mytestingdb          useNewUrlParser  true     then client   gt            The database name is part of the url   client db   seems         to know that and works even without a parameter that         relays the db name      let db   client db          console log  the current database is      db s databaseName          client close   if you want to      catch err   gt  console log err      My package json lists monbodb  3 2 5     The  useNewUrlParser  option is not required if you re willing to deal with a deprecation warning   But it is wise to use at this point until version 4 comes out where presumably the new driver will be the default and you won t need the option anymore

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Piggy backing on  MikkaS answer for Mongo Client v3 x  I just needed the async   await format  which looks slightly modified as this   const myFunc   async      gt             Prepping here             Connect     let client   await MongoClient connect  mongodb   localhost        let db   await client db            Run the query     let cursor   await db collection  customers   find              Do whatever you want on the result

User · Answer

I encountered the same thing  In package json  change mongodb line to  mongodb     2 2 33   You will need to npm uninstall mongodb  then npm install to install this version   This resolved the issue for me  Seems to be a bug or docs need to be updated

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I solved it easily via running these codes    npm uninstall mongodb --save   npm install mongodb 2 2 33 --save   Happy Coding

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I have MongoDB shell version v3 6 4  below code use mongoclient  It s good for me   var MongoClient   require  mongodb   MongoClient  assert   require  assert    var url    mongodb   localhost 27017 video   MongoClient connect url   useNewUrlParser  true    function err  client     assert equal null  err   console log  Successfully connected to server    var db   client db  video       Find some documents in our collection db collection  movies   find     toArray function err  docs       Print the documents returned docs forEach function doc    console log doc title          Close the DB client close           Declare success console log  Called find

[node.js] db.collection is not a function when using MongoClient v3.0

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