NodeJS Multer NGINX Upload Error: Unexpected token - in JSON at position 0

Question

I'm having trouble uploading an image using Multer to my NodeJS backend. I'm using Axios to POST FormData Object containing a image and some data to my NGINX proxy server which will eventually save it in my Digital Ocean Space. Everything works perfectly in my development environment but when I try to upload in the file in production I get this error:

SyntaxError: Unexpected token - in JSON at position 0
    at JSON.parse (<anonymous>)
    at createStrictSyntaxError ...

Since I'm only getting this error in production environment I feel like this has something to do with my nginx proxy setup (this is the only thing that differs from production to development).

Axois:

export async function createPost(formData) {
  axios.post(`${config.SERVER}/create_post`, formData, {
    headers: { Authorization: `Bearer ${localStorage.getItem("token")}` }
  });
}

Express & Multer:

const endpoint = new aws.Endpoint("sfo2.digitaloceanspaces.com/");

const s3 = new aws.S3({
  endpoint,
  accessKeyId: config.DO_SPACE_ACCESS_KEY,
  secretAccessKey: config.DO_SPACE_SECRET_KEY
});

var productionUpload = multer({
  storage: multerS3({
    s3,
    bucket: "bucket-name",
    acl: "public-read",
    contentType: multerS3.AUTO_CONTENT_TYPE,
    filename: (req, file, cb) => {
      cb(
        null,
        file.fieldname + "-" + Date.now() + `${path.extname(file.originalname)}`
      );
    }
  })
});

app.post(
  "/create_post",
  productionUpload.single("file"),
  verifyToken,
  create_post
);

Nginx Config:

 location  API/ {
        proxy_pass http://localhost:3000/;
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Content-Type 'application/json';

        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }

I've exhausted all option on this site and others. Thank you in advance!

Answer 1

This can be an issue as you are passing Content-Type as application/json and uploading a file whose content-type is not json. Remove this header and try it once