Building on what deb2fast said I would also pass in a couple of extra parameters to JSON.stringify() to get it to pretty format:
fs.writeFileSync('./data.json', JSON.stringify(obj, null, 2) , 'utf-8');
The second param is an optional replacer function which you don’t need in this case so null
works.
The third param is the number of spaces to use for indentation. 2 and 4 seem to be popular choices.