I have some checkbox inputs like so:

<input type="checkbox" name="1" class="filter"/>
<input type="checkbox" name="2" class="filter"/>
...etc...

I'm trying to write a function where any time a checkbox is selected, it generates a string with all the names concatenated. Here's what I have so far:

$('.filter').click(function(event){
    var filters = $('.filter').toArray();
    var fstr = "";
    for (f in filters)
    {
        fstr = fstr+","+f.name;
    }
    alert(fstr);
});

The names keep coming up as 'undefined', though (i.e. the alert returns ,undefined,undefined,undefined,undefined,undefined,undefined). How do I access the names?