This script was created with the intention of converting the Disqus backup XML file into a JSON that can be read successfully inside Node.js (since any other libraries seemed to crash with very large files ~350MB).
You can install it locally by running npm i disqus-xml2json, this allows it to run both standalone and as part of your own project.
To use it in standalone mode, after installing, simply run node ./node_modules/disqus-xml2json input-file.xml output-file.json.
If no filenames are provided, disqus.xml and disqus.json are used.
To use in your project, simply add const convert = require('disqus-xml2json') to your file and then, from your code, run convert(inputFile, outputFile, callback)
If you don't want to save the file, just get the list of threads as a raw array, use convert(inputFile, null, callback)
There are examples on how to process the JSON files included, one for general usage and other for WordPress usage.