xmlns,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
</head>
<body>
<select name="" size="5" multiple="multiple">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<script>
var o = $("option");
$.each([0, 1, 4],function(i, el){
o[el].selected="selected"
});
</script>
</body>
</html>