utils/language.js

   1 // Select a language based on browser preferences, or cookie
   2 module.exports = function(req, res)
   3 {
   4     // If preferred language already set:
   5     if (!!req.cookies["lang"])
   6         return req.cookies["lang"];
   7
   8     // Else: search and set it
   9     const supportedLang = ["en","es","fr"];
  10     const langString = req.headers["accept-language"];
  11     let langArray = langString
  12         .replace(/;q=[0-9.]+/g, "") //priority
  13         .replace(/-[A-Z]+/g, "") //region (skipped for now...)
  14         .split(",") //may have some duplicates, but removal is too costly
  15     let bestLang = "en"; //default: English
  16     for (let lang of langArray)
  17     {
  18         if (supportedLang.includes(lang))
  19         {
  20             bestLang = lang;
  21             break;
  22         }
  23     }
  24     // Cookie expires in 183 days (expressed in milliseconds)
  25     res.cookie('lang', bestLang, { maxAge: 183*24*3600*1000 });
  26     return bestLang;
  27 }