How to detect user input language in javascript?

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Javascript

I want to detect user input(numbers pad) language is English or Persian.
I'm using the following scripts but they work when user OS is Linux, but not when users OS is windows.

What I have tried:

first solution:

document.getElementById("num").addEventListener("keyup", 
          function(e) {
          var patt = new RegExp("^[\u06F0-\u06F9]+$");
          if (patt.test(e.key)) 
            document.getElementById("lang").innerHTML = "Persian";                            
          else 
            document.getElementById("lang").innerHTML = "english";
             })

Second solution:

document.getElementById('num').addEventListener('keypress',function(e){
      if (isPersian(e.charCode))
      document.getElementById("lang").innerHTML='Persian';
      else
      document.getElementById("lang").innerHTML='English';

         });

      function isPersian(charCode){
        return (charCode >= 1776 && charCode <= 1785) 
      }