Pantela,
http://api.jquery.com/serialize/
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
$(document).on("click", "[name=checkbox]", function(){
var c_pref = [];
$("[name=checkbox]:checked").attr('item_cat', function(i, item) {
c_pref.push(item)
});
c_pref += "";
alert(c_pref);
});
});
</script>
</head>
<body>
<input type="checkbox" name="checkbox" value="" item_cat="list">
<input type="checkbox" name="checkbox" value="" item_cat="food">
<input type="checkbox" name="checkbox" value="" item_cat="cars">
</body>
</html>