Simple smooth scrolling solution

smooscroll.js

var SmoothScroll = function () {

  'use strict';

  var self = this,
    $topReference = $('html, body'),
    $window = $(window)
  ;

  function targetPosition(targetHash) {
    // Escape any exclamation mark that might be present on the hash and is not a valid selector
    // e.g. "#!edit"
    targetHash = targetHash.replace(/(\!)/g, '\\$1');

    var verticalOffset = 10,
      topOffset = verticalOffset,
      $target = $(targetHash),
      position = 0
    ;

    return Math.round( ( $target[0] ? $target.offset().top : 0 ) - topOffset );
  }

  function goToTarget(targetHash) {
    var yCoord;
    if (targetHash) {
      yCoord = targetPosition(targetHash);

      // Triggering it right away fixes ambiguos behavior on IE9
      window.scrollTo(0, yCoord);
      // Safari needs a small delay before you can execute the scroll position
      // This is way the scrolling is triggered again after a brief delay
      setTimeout(function () {
        $window.scrollTop(yCoord);
      }, 1);
    }
  }

  function pushHistoryState(targetHash) {
    if (Modernizr.history) {
      var location = window.location,
        pathSegments = location.pathname.split(/\//g),
        path = pathSegments[pathSegments.length],
        stateObj = {},
        title = '',
        url = location.pathname + location.search + targetHash
      ;

      stateObj[path] = targetHash.replace(/^#/, '');
      history.pushState(stateObj, title, url);
    }
  }

  function scrollHandler(event) {
    event.preventDefault();
    var targetHash = $(this).attr('href'),
      duration = 800,
      easing = 'swing',//'easeOutQuad',
      position = targetPosition(targetHash)
    ;

    $topReference
      .stop()
      .animate({scrollTop: position}, duration, easing, function () {
        pushHistoryState(targetHash);
      })
    ;
  }

  /**
   * @constructor
   */
  self.initialize = function () {
    $('.js-smoothscroll').on('click', scrollHandler);
    goToTarget(window.location.hash);
  }

  self.initialize();

}