scrollToElement.js

(function() {
  var defaultDuration = 500;

  var scrollToElement = function($element, duration) {

    // use body if no $element is defined
    // use fdefault duration if is not sad different
    $element = $element || $('body');
    duration = duration || defaultDuration;

    // stop if the is no such element
    if ($element.length === 0) return false;

    // set offset (with navbar height)
    var offset = $element.offset().top - $('#nav-bar').outerHeight();

    // scroll
    $('html, body').animate({
      scrollTop: offset
    }, duration);
  };

  // jquery function
  $.fn.scrollToElement = function(duration) {
    scrollToElement($(this), duration);
  };

  // default use on this class
  $('a.scroll-to').on('click', function(e) {
    e.preventDefault();

    var selector = $(this).attr('href');

    $(selector).scrollToElement();
  });
})();