//Try the following code
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("#click").click(function(){
var divContent = $('#field').text();
var res = divContent.substring(2,3);
$("#display").text(res);
alert(res );
});
});
</script>
</head>
<body>
<div id="field">23*34</div><br>
<div id="display"></div><br>
<button id="click">click for value</button >
</body>
</html>