node.js i18n: Use __ or import?

I am new to i18n and have an existing repository that uses it. I noticed different syntax for using i18n throughout the repository and am wondering what is the best way.

I am confused about the structure below and which syntax option is best (I think it's better to be consistent with the syntax and use only 1 option). Could someone perhaps explain?

In controllers I find:

var responses = require('../../locales/en.json');

let message = responses.authorisation.flashes['welcome'];
return res.status(200).json({
  success: true,
  message,
  token,
  user: userData
});

In middleware the syntax is as follows:

req.flash('error', req.__('organisation.not-found'));

And in app.js I find:

const flash = require('connect-flash');
const flashMiddleware = require('./middleware/flashMiddleware');

const i18n = require('i18n');
i18n.configure({
  locales: [
    'en', 'nl'
  ],
  register: global,
  directory: path.join(__dirname, 'locales'),
  defaultLocale: 'en',
  objectNotation: true,
  updateFiles: false
});

flashMiddleware.js contains (I'm not sure what this does):

const flashMiddleware = (req, res, next) => {
  res.locals.flashes = req.flash();

  next();
};

module.exports = flashMiddleware;