google-api-nodejs-client examples using JWT and service account

drive-api-test

const README = '\n\nThis script is intended to help you use a google API  \
client_secret.json file to obtain an OAUTH token (json data) and \
store it next to the source .json for future use. \n\n\
To acomplish this, you will be given an URL that you can follow to  \
get a "code" which can then be used to get a token. As an I/O solution \
I run this script with `node --inspect-brk` and then I catch the debugger \
after the URL is logged to the console. Once I have the code, I can run \
`code="{codeFromUrl}"` and resume the script. \n\n\n';
console.log( README );

// process.env.PATH_TO_CLIENT_SECRET_JSON is expected to have a valid path to a OAuth/Other/client_secret.json 
//  as provided by the steps at https://console.cloud.google.com/apis/credentials. A detailed tutorial can be
//  found in Step 1 at https://developers.google.com/drive/v3/web/quickstart/nodejs.

const path = require('path'),
    fs = require('fs'),
    keyfile = path.normalize(path.join(__dirname, process.env.PATH_TO_CLIENT_SECRET_JSON )),
    tokenfile = keyfile.replace(/\.json$/g, '') + '.token';
    keys = JSON.parse(fs.readFileSync(keyfile)),
    scopes = ['https://www.googleapis.com/auth/drive'],
    google = require('googleapis');

let client = new google.auth.OAuth2(
      keys.web.client_id,
      keys.web.client_secret,
      keys.web.redirect_uris[0]
    ),
    code = null;

//Start with node --inspect-brk so you have time to hit this then retrieve the code and `code='{yournewcode}'` in the console
console.log( '\nGet code from:\n\n' + client.generateAuthUrl( { access_type: 'offline', scope: scopes } ) );
console.log( '\nWhen you have that code, return and run `code="yourNewCode"` in the console and resume the debugger.\n\n' );

debugger;

Updated after my 3rd attempt in 2 years to get Drive support in my node app, but being thwarted by volumes of confusing documents, conflicting examples and various approaches. As of 2018-05-09, this approach is "current" in that is uses the latest approach from the console, but it uses API v25 because v29 breaks completely with these samples and I can't find any docs that address those issues.