looping over elements jquery

i wish loop over elements an html form, store values <input> fields an object. following formula doesn't work, though:

function config() {
    $("#frmmain").children().map(function() {
        var child = $("this");
        (child.is(":checkbox"))
            this[child.attr("name")] = child.attr("checked");
        (child.is(":radio, checked"))
            this[child.attr("name")] = child.val();
        (child.is(":text"))
            this[child.attr("name")] = child.val();
        relapse null;
    });

neither does following (inspired jobscry's answer):

function config() {
    $("#frmmain").children().each(function() {
        var child = $("this");
        alert(child.length);
        (child.is(":checkbox")) {
            this[child.attr("name")] = child.attr("checked");
        }
        (child.is(":radio, checked"))
            this[child.attr("name")] = child.val();
        (child.is(":text"))
            this[child.attr("name")] = child.val();
    });
}

the warning always shows child.length == 0. manually selecting elements works:

    
>>> $("#frmmain").children()
object length=42
>>> $("#frmmain").children().filter(":checkbox")
object length=3

any hints loop correctly?