The "chunk" argument must be of type string or an instance of Buffer

Question

I'm running the following code and it fails with the below error.

AWS Code to list all objects inside a bucket.

const http = require('http');
const host = '127.0.0.1';
const port = 5000;
const path = require('path');
const url = require('url');
const fs = require('fs');
var AWS = require('aws-sdk');



const laptopDate = JSON.parse(fs.readFileSync(`${__dirname}/data/data.json`, `utf-8`));

AWS.config.update({accessKeyId: '***', secretAccessKey: '***', region: 'ap-south-1'});
s3 = new AWS.S3({apiVersion: '2006-03-01'});

var params = { 
    Bucket: 'bucket-name'
};

const server = http.createServer(function(req, res){
    const path = url.parse(req.url, true).pathname;
    const id = url.parse(req.url, true).query.id;

    if (path === 'bucket' || path === '/')
      s3.listObjects(params, function (err, data) {
        if(err) throw err;
        res.writeHead(200, { 'Content-Type': 'text/html' });
        //const output = JSON.parse(data)
        console.log(data);
        res.end(data);
      });
});

server.listen(port, host, function(req, res) {
    console.log(`Server is listening on ${host} and ${port}`)
});

The first output which is console.log displays everything as expected. However the res.end to render the output to the screen fails with the below error.

The "chunk" argument must be of type string or an instance of Buffer. Received an instance of Object
    at ServerResponse.end (_http_outgoing.js:752:13)
    at Response.<anonymous> (D:\js\Extra\starter\index.js:30:13)
    at Request.<anonymous> (D:\js\Extra\starter\node_modules\aws-sdk\lib\request.js:364:18)
    at Request.callListeners (D:\js\Extra\starter\node_modules\aws-sdk\lib\sequential_executor.js:106:20)
    at Request.emit (D:\js\Extra\starter\node_modules\aws-sdk\lib\sequential_executor.js:78:10)
    at Request.emit (D:\js\Extra\starter\node_modules\aws-sdk\lib\request.js:683:14)
    at Request.transition (D:\js\Extra\starter\node_modules\aws-sdk\lib\request.js:22:10)
    at AcceptorStateMachine.runTo (D:\js\Extra\starter\node_modules\aws-sdk\lib\state_machine.js:14:12)
    at D:\js\Extra\starter\node_modules\aws-sdk\lib\state_machine.js:26:10
    at Request.<anonymous> (D:\js\Extra\starter\node_modules\aws-sdk\lib\request.js:38:9) {
  message: 'The "chunk" argument must be of type string or an instance of Buffer. Received an instance of Object',
  code: 'ERR_INVALID_ARG_TYPE',
  time: 2020-05-18T08:39:24.916Z
}

Answer 1

Remove this res.writeHead(200, { 'Content-Type': 'text/html' });

And instead of res.end(data) use res.send(data) or better yet res.send({ data }).

---

EDIT I didn't notice that you didn't use express, try this:

res.writeHead(200, { 'Content-Type': 'application/json' });
res.write(JSON.stringify(data));
res.end();

Answer 2

In case this may help someone, try to use the objectMode propertie.

somthing like it

const t = new Transform({
    objectMode: true, // set this one to true
    transform(data, _, done) {
      //...your code
    }
  });

Answer 3

In case this may help someone, I was using data type other than String, Number to be exact, so I changed it to String to resolve this error