const express = require('express')
const app = express()
const uuidv4 = require('uuid/v4');

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

var ReqNullChecker = (req) => {
  var params = req.params.some( (params) =>{ if ( params==null ) { return true } else { return false } } )
  req.ReqNullChecker = params
  next();
};

app.use(ReqNullChecker);

app.get('/login/:username/:password', function(req, res){

    if (req.ReqNullChecker == true){
      MongoClient.connect(url, function(err, db) {
        var dbo = db.db("test");
        dbo.collection("users").findOne({ username: req.params.username }, function(err, result) {
            if (result.password==req.params.password){
                var randomsession = uuidv4();
                dbo.collection("users").updateOne({ _id: result._id }, { $set: { sessionid: uuidv4() } }, function(err, res) {
                    res.send('user session' + randomsession );
                });
            }
            else{
                console.log("False")
            }
            db.close();
        });
      });
    }

});



app.listen(3000, () => console.log('Example app listening on port 3000!'))

I get error :(((
TypeError: req.params.some is not a function
    at ReqNullChecker (/Users/seal/Desktop/app.js:9:27)
    at Layer.handle [as handle_request] (/Users/seal/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/Users/seal/node_modules/express/lib/router/index.js:317:13)
    at /Users/seal/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/Users/seal/node_modules/express/lib/router/index.js:335:12)
    at next (/Users/seal/node_modules/express/lib/router/index.js:275:10)
    at expressInit (/Users/seal/node_modules/express/lib/middleware/init.js:40:5)
    at Layer.handle [as handle_request] (/Users/seal/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/Users/seal/node_modules/express/lib/router/index.js:317:13)
    at /Users/seal/node_modules/express/lib/router/index.js:284:7