Turkish key replacement for duolingo. Install this script in the Tampermonkey extension in Chrome.

key-replace.js

// ==UserScript==
// @name         Turkish key replacement
// @namespace    http://example.com/
// @version      0.1
// @description  Type a backtick (`) after a letter to get the turkish variation.
// @author       Simon Hobbs
// @match        https://www.duolingo.com/skill/*
// @grant        none
// ==/UserScript==

$(window).keyup(function() {
    if (event.which == 192) {
        $focus = $(':focus');
        text = $focus.val();
        start = $focus[0].selectionStart;
        character = text.substring(start-2, start);
        new_char = match_char(character);
        new_text = text.substring(0,start-2) + new_char + text.substring(start, text.length);
        $focus.val(new_text);
    }
}); 

function match_char(char) {
  switch (char) {
    case 'c`':
      return 'ç';
    case 'i`':
      return 'ı';
    case 'o`':
      return 'ö';
    case 's`':
      return 'ş';
    case 'u`':
      return 'ü';
  }
  return char;
}