TypeError: Cannot read property 'length' of undefined node.js

Question

I am trying to insert multiple data into mongoDB. Data comes from another web service in JSON format. I collect that data and store in my DB. But, when I am trying to iterate over collected items, I get Type Error as mentioned in Question.

// Add purchase details to DB (Userid, Productid, Category)
router.post('/addpurchased', function(req, res){
    // Connect to the server
    MongoClient.connect(url, function(err, db){
      if (err) {
        console.log('Unable to connect to the Server:', err);
      } else {
        console.log('Connected to Server',url);


    // Get the documents collection
    var collection = db.collection('purchased');

    var arrProducts = req.body.products;
    var userProducts = [];

    for(var i = 0; i < arrProducts.length; i++){
      // Get the purchased details passed from the form
      var user = {userid: arrProducts[i].userid, productid: arrProducts[i].productid, category: arrProducts[i].category,
         purchasetime: new Date()};

      userProducts.push(user);
    }

    // Insert the purchase data into the database
    collection.insert(userProducts, function (err, result){
      if (err) {
        console.log(err);
      } else {
        res.send("Purchase Details Added")
      }
    });
  }
});

});

Please let me know what I am missing here.

I am passing JSOM data from postman as below,

and get error message as below.

Answer 1

As others mentioned in comments, your req.body.products is comming in null. This will fix your error, but then you need to figure out why you are not getting products.

 var arrProducts = [];
  if(req && req.body && req.body.products){
   var arrProducts = req.body.products;
  }

  for(var i = 0; i < arrProducts.length; i++){
  // Get the purchased details passed from the form
  var user = {userid: arrProducts[i].userid, productid: arrProducts[i].productid, category: arrProducts[i].category,
     purchasetime: new Date()};

  userProducts.push(user);
}

You can do that by printing out the contents of body to debug or

console.log(req.body);

Answer 2

You have wrong JSON format in postman. Use inverted commas in JSON format as request requires it to be as a string.

If you will use this from Javascript XHR request you need to use JSON.stringify(object) before sending request to server.

{ 
"products": [
       {
        "productid" : "first",
        "userid" : "1",
        "category": "edu"
       },
       {
        "productid" : "second",
        "userid" : "2",
        "category": "edu"
       }
]
}

Answer 3

Thanks for the leads. I was not passing JSON data properly. Now it works fine.