Slide-scroll on page with jQuery

gistfile1.js

(function($){
  $.fn.scrollTo = function(maxTime, callback){
    if(typeof maxTime === "function"){
      callback = maxTime;
      maxTime = 2000;
    }else if(!maxTime){
      maxTime = 2000;
    }
    if(!callback){
      callback = new Function();
    }
    
    var dest_pos = $(this).offset().top;
    var distance = dest_pos - $(document).scrollTop();//down is positive
    var done = false;
    $('body,html').animate({ scrollTop: dest_pos }, Math.min(maxTime, Math.abs(distance)), function(){
      if(!done){
        done = true;
        callback.call(this);
      }
    });
  };
})(jQuery);

$(document).ready(function(){
  $('a[href^="#"]').click(function(e){
    e.preventDefault();
    var dest = $(this).attr('href');
    $(dest).scrollTo(700, function(){
      window.location.hash = dest.substr(1);
    });
  });
});