utf8_2_utf16.js

'use strict';

const path = process.argv[2];
if (!path) {
  console.log('Add the file path, please.');
  process.exit();
}

const fs = require('fs');

fs.createReadStream(path, {encoding: 'utf8'})
  .pipe(fs.createWriteStream(path.replace(/(\.[^.]+)?$/, '.utf16$1'), {encoding: 'utf16le'}));