Edge Case Mobile Nav where the child is relative to a smaller parent. Use this if you want that child to be the full width of the window.

full-width-nav.js

var $window = $(window);
var $daNav = $('.main-head__nav').find('.menu');

function navGrow() { //it's like miracle grow for navs.
    var superWide = $window.width();
    $daNav.css('width', superWide);
    $('.main-head__nav').click(function () {
        $daNav.toggleClass('clack');
    });
    if ($window.width() > 768) {
        if ($daNav.hasClass('clack')) {
            $daNav.removeClass('clack');
        }
        $daNav.css('width', '');
    }
}
$window.load(navGrow);
$window.resize(function () {
    $daNav.css('width', '');
    $daNav.removeClass('clack');
    navGrow();
});