<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){   
	$(".replace").on("keyup", function(){
			str = $(this).val();
			var dizi = { "İ": "I", "Ş": "S", "Ğ": "G", "Ü": "U", "Ö": "O", "Ç": "C",  "ş": "s", "ğ": "g", "ü": "u", "ö": "o", "ç": "c" };
			str = str.replace(/(([İŞĞÜÖÇşğüöç]))+/g, function(harf){ return dizi[harf]; })
			$(this).val(str);
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});
</script>
<input type="text" value="" style="width:300px;" class="replace" name="deneme" id="deneme" />