Quick test:

  ron? snn
  fra? cat
  swe? nds
  ita? und
  nld? gax

Source:

  var franc = require('franc');
  console.log('ron?', franc('Cate bere ai baut?'));
  console.log('fra?', franc('C\'est quoi le bordel la, putain'));
  console.log('swe?', franc('Jag kanner en bot, hon heter Anna'));
  console.log('ita?', franc('che guai'));
  console.log('nld?', franc('graag gedaan'));