checkbox can not checked or uncheck by directly click on checkbox?

checkbox can not checked or uncheck by directly click on checkbox ?

i was create click on div for toggle checked/unchecked checkbox. this function was best.

But when i tried to click on checkbox directly, i can not check or uncheck checkbox.

How can i do that ?

http://ift.tt/1XmeaXV

<script>
function onclick_cover_checkbox_fn(){
    var main_checkbox_checked_uncheck_var = document.getElementById("main_checkbox_checked_uncheck");
    var main_checkbox_checked_uncheck_var_checked_status = main_checkbox_checked_uncheck_var.checked;

    if(main_checkbox_checked_uncheck_var_checked_status != true)
    {
        document.getElementById("main_checkbox_checked_uncheck").checked = true;
        checked_all_or_uncheck_all_fn();
    }
    else
    {
        document.getElementById("main_checkbox_checked_uncheck").checked = false;
        checked_all_or_uncheck_all_fn();
    }
}
</script>

<script>
function checked_all_or_uncheck_all_fn(){
    alert("5555");
}
</script>