$(document).ready(function() {
  $(".disaster-checkbox").change(function () {
    // if all-disasters checked, uncheck all others (save state checkboxes)
    if ($(this).val() == "all-disasters" && $(this).is(":checked")) {
        $("#all-disasters-checkbox").prop("checked",false);
        $(".disaster-checkbox").each(function(){ $(this).data("restore", $(this).is(":checked")); });
        $(".disaster-checkbox").removeAttr("checked");
        $("#all-disasters-checkbox").prop("checked",true);

    // if all-disasters unchecked, restore what was checked
    } else if ($(this).val() == "all-disasters" && !$(this).is(":checked")) {
        $(".disaster-checkbox").each(function(){ $(this).prop("checked",$(this).data("restore")); });
        // if nothing is selected, select each disaster
        if (!$(".disaster-checkbox").is(":checked")) $(".disaster-checkbox").each(function(){ $(this).prop("checked",true); });
        $("#all-disasters-checkbox").prop("checked",false);

    // if anything other than all-disasters is checked, uncheck all-disasters (unless nothing is checked)
    } else if ($(this).val() != "all-disasters") {
        var uncheck = false;
        $(".disaster-checkbox").each(function(){
            if ($(this).is(":checked") && $(this).val() != "all-disasters") uncheck = true;
        });
        if (uncheck) $("#all-disasters-checkbox").prop("checked",false);
        else $("#all-disasters-checkbox").prop("checked",true);
    }
  });
});