Can't call any fineUploader methods in callback function

I have autoUpload set to false, as I want to upload the images myself to my backend. However, to do this I first need the file object. In the callbacks onSubmitted event I'm trying to pass the images id to the getFile method, to return the object. However, when I try to do this I get the below error message.

in onSubmitted: id=0 | name=28603454_15219061700_r.jpg index.js:2178

[Fine Uploader 5.16.2] Caught exception in 'onSubmitted' callback - Cannot read property 'uploader' of null

I'm guessing I get this because I'm declaring a const object and referencing it at the same time, which I believe you cannot do...

So, any ideas on how I can call methods within the callbacks function? Or is there another way?

const uploader = new FineUploaderTraditional({
  options: {
    maxConnections: 1,
    autoUpload: false,
    deleteFile: { enabled: true, endpoint: "/uploads" },
    request: { endpoint: "/uploads" },
    retry: { enableAuto: true },
    callbacks: {
      onSubmitted: function(id, name) {
        console.log("in onSubmitted: id=" + id + " | name=" + name);
        // getFile(id) returns a `File` or `Blob` object.
        console.log(this.uploader.getFile(id));
      }
    }
  }
});

Update I've now taken all of my fine-uploader code and created a new component with it. I'm still facing the same problems. Starting a bounty. Component code below:

FineUploader.jsx

import React, { Component } from "react";
import FineUploaderTraditional from "fine-uploader-wrappers";
import Gallery from "react-fine-uploader";
import Filename from "react-fine-uploader/filename";
import "react-fine-uploader/gallery/gallery.css";

const util = require("util");

const uploader = new FineUploaderTraditional({
  options: {
    // debug: true,
    maxConnections: 1,
    autoUpload: false,
    deleteFile: { enabled: true, endpoint: "/uploads" },
    request: { endpoint: "/uploads" },
    retry: { enableAuto: true },
    validation: {
      acceptFiles: ".jpg,.png,.gif,.jpeg",
      allowedExtensions: ["jpg", "png", "gif", "jpeg"],
      itemLimit: 5,
      sizeLimit: 5000000
    },
    callbacks: {
      onCancel: function() {
        console.log("in onCancel: ");
      },
      onComplete: function(id, name, responseJSON, xhr) {
        console.log("in onComplete: " + id + " | " + name + " | " + responseJSON + " | " + xhr);
      },
      onAllComplete: function(succeeded, failed) {
        console.log("in onAllComplete: " + succeeded + " | " + failed);
      },
      onProgress: function(id, name, uploadedBytes, totalBytes) {
        console.log("in onProgress: " + id + " | " + name + " | " + uploadedBytes + " | " + totalBytes);
      },
      onError: function(id, name, errorReason, xhr) {
        console.log("in onError: " + id + " | " + name + " | " + errorReason + " | " + xhr);
      },
      onDelete: function(id) {
        console.log("in onDelete: " + id);
      },
      onDeleteComplete: function(id, xhr, isError) {
        console.log("in onDeleteComplete: " + id + " | " + xhr + " | " + isError);
      },
      onPasteReceived: function(blob) {
        console.log("in onPasteReceived: " + blob);
      },
      onResume: function(id, name, chunkData, customResumeData) {
        console.log("in onResume: " + id + " | " + name + " | " + chunkData + " | " + customResumeData);
      },
      onStatusChange: function(id, oldStatus, newStatus) {
        console.log("in onStatusChange: " + id + " | " + oldStatus + " | " + newStatus);
      },
      onSubmit: function(id, name) {
        console.log("in onSubmit: " + id + " | " + name);
      },
      onSubmitted: function(id, name) {
        console.log("in onSubmitted: id=" + id + " | name=" + name);
        // getFile(id) returns a `File` or `Blob` object.
        // console.log(this.uploader.getFile(id));
        // console.log(uploader.getFile(id));
        // nothing here is working.... :(
      },
      onUpload: function(id, name) {
        console.log("in onUpload: " + id + " | " + name);
      },
      onValidate: function(data, buttonContainer) {
        console.log(
          "in onValidate: " + util.inspect(data, { showHidden: true, depth: null }) + " | " + buttonContainer
        );
      },
      onSessionRequestComplete: function(response, success, xhrOrXdr) {
        console.log("in onSessionRequestComplete: " + response + " | " + success + " | " + xhrOrXdr);
      }
    }
  }
});

const fileInputChildren = <span>Click to Add Photos</span>;
const statusTextOverride = {
  upload_successful: "Success!"
};

class FineUploader extends Component {
  constructor() {
    super();

    this.state = {
      submittedFiles: []
    };
  }

  componentDidMount() {
    uploader.on("submitted", id => {
      const submittedFiles = this.state.submittedFiles;
      console.log("submittedFiles: " + submittedFiles);

      submittedFiles.push(id);
      this.setState({ submittedFiles });
    });
  }

  render() {
    return (
      <div>
        {this.state.submittedFiles.map(id => (
          <Filename id={id} uploader={uploader} />
        ))}
        <Gallery
          fileInput-children={fileInputChildren}
          status-text=
          uploader={uploader}
        />
      </div>
    );
  }
}

export default FineUploader;

And -- On the main page now, I'm importing FineUploader.jsx, and using the component.

import FineUploader from "../../components/FineUploader";

In my render method I have:

<FineUploader />

from Can't call any fineUploader methods in callback function