URLをParseして、適当にクラスをつける。適当実装。

parse.coffee

do($=jQuery) =>

    $(".l-navigation__item").find("a").each ->
      origin = location.origin
      href = @.href.replace origin, ""
      dir = href.replace "index.html", ""
      if dir == "/" or dir == ""
        #TOPの場合。
        pathname = location.pathname.replace "index.html", ""
        if pathname == "/" or pathname == ""
          $(@).addClass("current")
      else
        #通常の処理
        if location.pathname.indexOf(dir) != -1
          $(@).addClass("current")
        #URL構造と、サイト構造が合っていない場合。。。/hogeにいるときに、piyoへのリンクをcurrentへ
        else if location.pathname.indexOf("/^hoge/") == 0 and dir.indexOf("piyo") != -1
          $(@).addClass("current")

(function(_this) {
  return (function($) {
    return $(".l-navigation__item").find("a").each(function() {
      var dir, href, origin, pathname;
      origin = location.origin;
      href = this.href.replace(origin, "");
      dir = href.replace("index.html", "");
      if (dir === "/" || dir === "") {
        pathname = location.pathname.replace("index.html", "");
        if (pathname === "/" || pathname === "") {
          return $(this).addClass("current");
        }
      } else {
        if (location.pathname.indexOf(dir) !== -1) {
          return $(this).addClass("current");
        } else if (location.pathname.indexOf("/^hoge/") === 0 && dir.indexOf("piyo") !== -1) {
          return $(this).addClass("current");
        }
      }
    });
  });
})(this)(jQuery);