Ajax hash navigation with default page switch and transition animation

hashnav.js

var container_div = ".container", content_div = ".content", default_hash = "#main";

function anchorRefresh() {
  var a = location.hash.substring(1);
  $(".active").removeClass("active");
  $(content_div).css({opacity:0.5});
  $(content_div).load("ajax/" + a + ".html", function() {
    $(location.hash).addClass("active");
    $(content_div).animate({opacity:1})
  })
}

$(window).on("hashchange", function() {
  anchorRefresh()
});

"" == location.hash ? location.hash = default_hash : anchorRefresh();