express / nodejs：停止发布请求中的重复项

Question

What should I do to stop the post request from posting new object if the object already exists? I have pasted my code and json object. I have tried next(); but it doesnt work and a duplicate object with some other id is created no matter what. I am using before beforePostTransaction function to check if the product already exists. The request contains the id and the store id of the

index.js

const Transaction = require('./transactions/TransactionModel');
const TransactionCTL = require('./transactions/TransactionController');
Transaction.before('post', TransactionCTL.beforePostTransaction);
Transaction.register(router, '/transactions');

TransactionController.js

const beforePostTransaction = (req, res, next) => {
var id = req.body.id;
Transaction.findById(
    id, 
    (err, data)=>{
        if (!data){
            next();
        }
        else{

            var store = data.store;
            store = JSON.stringify(store);
            store = store.replace(/\"/g, "");
            if(store !== req.body.store){ //update the whole object
                next();
            }
            else{
            //do what?
            }

        }
    });
    res.sendStatus(409);
}

json object

[{
    "_id": "596db06849822a13c97ba3f9",
    "store": "596b088131ea400490897c50"
}]

Answer 1

Not sure what is your model. But if it is mongoose you can use method

.findOneAndUpdate(query,
        update,
        {upsert: true},
        function (error, result) {
          if (!error) { //if you need to do something else
          }
        });

Where update is your object. It will create new item if it not exist and update it if it exist.