how to detect user's language while he/she is typing

Question

guys i have a problem with this thing , i must know which language the user is using while typing in an input text to handle some bad shaped things and i even looked at this in here but it didn't helped me , can u guys help me with the right code ?
the languages i must know are english and persian :| thanks :) i need some javascript helps

<input type="text" id="give_me_the_lang">
<div id="show_lang_in_here"></div>

Answer 1

Here is the solution that doesn't really detect language, but just checks if users input contains only English alphabet. If it does, it writes "English" in div, otherwise it writes "Persian". Code:

document.getElementById("give_me_the_lang").addEventListener("keyup", function() {
  if (/^[a-zA-Z]+$/.test(this.value)) {
    document.getElementById("show_lang_in_here").innerHTML = "English";
  } else {
    document.getElementById("show_lang_in_here").innerHTML = "Persian";
  }
});

<input type="text" id="give_me_the_lang">
<div id="show_lang_in_here"></div>

Expression ^[a-zA-Z]+$ only checks the letters of English alphabet, if you write in number or any other character, the result will be "Persian".