dw/js/_init.js

$(function () {
  header();
  hamburger();
});

function header() {
  var $window = $(window),
  $smallHeader = $('.header-small'),
  smallHeaderShowing = false;

  function small_header() {
    var top = $window.scrollTop();
    if (top > 200 && !smallHeaderShowing) {
      $smallHeader.addClass('showing');
      smallHeaderShowing = true;
    }
    else if (top <= 200 && smallHeaderShowing) {
      $smallHeader.removeClass('showing');
      smallHeaderShowing = false;
    }
  }

$window.scroll(small_header);
small_header();
}

function hamburger() {
var isOpen = false,
  $hamburger = $('.hamburger'),
  $headerSmall = $('.header-small');

  $hamburger.on('click', function () {
    isOpen = !isOpen;
    $hamburger.toggleClass('is-active');
    $headerSmall.toggleClass('menu-open');
  });

  $(window).on('scroll', function(){
    if(isOpen){
      $hamburger.removeClass('is-active');
      $headerSmall.removeClass('menu-open');
      isOpen = false;
    }
  });
}