TypeError: Cannot read property '0' of undefined in post method in nodejs

user_15523221 0
Viewed 1012

I am new to nodejs and mongodb. I am trying to create simple to-do app with nodejs and mongodb. I have added the task in database. Now in post method, I am using insertOne method of mongodb and in res.json I am having the following error.

res.json(info.ops[0].data)
TypeError: Cannot read property '0' of undefined

Code :

app.post('/create-item', function(req, res){
    db.collection('items').insertOne({ text:req.body.text }, function(err, info){
      res.json(info.ops[0])
    })
})

Below is the screenshot of Error. Error Screenshot

node.js mongodb javascript
3 Answers

In current versions, there is no property returned named ops when insertOne is successful.

Hence the error TypeError: Cannot read property '0' of undefined

insertOne returns two properties:

acknowledged
Indicates whether this write result was acknowledged. If not, then all other members of this result will be undefined
insertedId
The identifier that was inserted. If the server generated the identifier, this value will be null as the driver does not have access to that data

See:

app.post('/create-item', function(req, res){
    db.collection('items').insertOne({ text:req.body.text }, function(err, info){
      console.log(info.acknowledged)
       console.log(info.acknowledged)
      res.json(info.acknowledged)
    })
})

In previous versions, for example 3.2, different properties were returned for insertOne:

Similarly, different properties were returned for updateOne:

For more information about migrating to version 4 from earlier versions, see the article:

Changes in 4.x (and how to migrate!)

user_41547060

I encountered the same problem with the to-do app tutorial today. For those interested try changing the line - res.json(info.ops[0])

to - res.json({ _id: info.insertedId.toString(), text: req.body.text })

This gets the inserted id from the database for the newly added item. As "info" doesn't seem to return the inserted text in the current version of mongodb - i added that from the request parameter.

I got my information from here - Get the _id of inserted document in Mongo database in NodeJS

user_149650240

you are doing it wrong way firstly check the err then send the res.json because the error is because your info might be null if data not inserted successfully so you need to do it like

app.post('/create-item', function(req, res){
    db.collection('items').insertOne({ text:req.body.text }, function(err, info){
      if (err) {
           res.json({message: "not inserted successFully"});
           return;
       }
      res.json(info.ops[0])
    })
})

now in above code what will happen if data is not inserted successfully it will send the error as response and return from function.

user_117435370
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