This is a stand alone NodeJS script that flattens a JSON file to CSV format. It does not require a schema definition a priori. However, it does assume that the JSON file is of consistent format throughout. If not, the produced CSV will be wrong.

More details here.

You will need the traverse package.

npm install traverse

node convertJsonToCsv.js /path/to/input/file.json

Produced CSV will be pushed to stdout.