Files Uploaded to S3 do not open

I was developing nodejs api to upload file to my AWS s3. I followed some online articles and using the code below. The files (images/word/pdf) get successfully uploaded to s3. However they do not open. Or give error when downloading and opening in local. One thing noticed here is that files uploaded through my web app have the metadata content-type:"application/octet-stream" while files uploaded manually to s3 have metadata content-type:"image/jpeg". Am I missing something. Here is my nodejs api:

    app.post("/uploadfile", upload.single("file"), async (req, res) => {
      try {
        console.log(req.file);
        var file = req.file;
    
        const fileStream = fs.createReadStream(file.path);
    
        const params = {
          Bucket: bucketName,
          Key: file.originalname,
          Body: fileStream,
        };
        const result = await s3.upload(params).promise();
        return res.status(200).send({
          ok: true,
          message: "File upload successful",
          location: result.Location,
        });
      } catch (err) {
        res.status(500).send({
          ok: false,
          message: "Failed to upload file. Error: " + err.message,
        });
      }
    });

Front end code:

const [file, setFile] = useState();
  const onSubmit = async (data) => {
    console.log(data);
    const fileData = new FormData();
    fileData.append("file", file);

    const uploadResult = await uploadFile(fileData);
    console.log(uploadResult);
}

const uploadFile = async (data) => {
  const requestOptions = {
    method: "POST",
    body: data,
  };
  const endPoint = DEV_API_URL + "uploadfile";
  const response = await fetch(endPoint, requestOptions);
  const responseJson = await response.json();
  return responseJson;
};