Your code does not make sense, see my demo code below:
<!DOCTYPE html>
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("#getSelectedValue").click(function(){
$('#multiselect :selected').each(function(i, selected) {
alert($(selected).val());
});
});
});
</script>
</head>
<body>
<select id="multiselect" multiple>
<option value="11">11</option>
<option value="22">22</option>
<option value="33">33</option>
</select>
<br><br>
<input type="button" id="getSelectedValue" value="Show Selected Values" >
</body>
</html>
Suggest you read out on the following topics:
HTML[
^]
JavaScript[
^]
jQuery[
^]