Getting "first argument must be a string or Buffer" error

The error is in the request call. To submit the form correctly use

    request.post({        url: 'http://localhost:5000/generate',        form: formatted    }, function(error, response, body) {        console.log(body);    });

I encourage you to use the npm module request-promise-native:https://github.com/request/request-promise-nativehttps://www.npmjs.com/package/request-promise

var rp = require('request-promise');var options = {    method: 'POST',    uri: 'http://api.posttestserver.com/post',    body: {        some: 'payload'    },    json: true // Automatically stringifies the body to JSON };rp(options)    .then(function (parsedBody) {        // POST succeeded...     })    .catch(function (err) {        // POST failed...     });

your body is expected to be Buffer try this, json:true in request option

 request.post({        headers: {            'content-type': 'application/x-www-form-urlencoded'        },        url: 'http://localhost:5000/generate',        body: formatted,        json:true    }, function(error, response, body) {        console.log(body);    });

why are you writing:

router.route('/function')  .post(function(req, res) {

try:

router.post('/function', function(req, res) {