[Guliashik]

<script type="text/javascript" src="scripts/alphabet.js"></script>
            <script type="text/javascript">
                window.alert(tatarcha.alphabet.keyboard[0][0].value);
                tatarcha.alphabet.keyboard[0][0].value='а';
                window.alert(tatarcha.alphabet.keyboard[0][0].value);
            </script>
        </form>
    </body>

Вот так работает.