smooth scroll

gistfile1.js

'use strict';

/**
 * @ngdoc service
 * @name myApp.anchorSmoothScroll
 * @description
 * # anchorSmoothScroll
 * Service in the myApp.
 */
angular.module('myApp')
.service('anchorSmoothScroll', function ($document, $window) {

  var document = $document[0];
  var window = $window;

  function getCurrentPagePosition(window, document) {
    // Firefox, Chrome, Opera, Safari
    if (window.pageYOffset) {return window.pageYOffset;}
    // Internet Explorer 6 - standards mode
    if (document.documentElement && document.documentElement.scrollTop){
      return document.documentElement.scrollTop;
    }
    // Internet Explorer 6, 7 and 8
    if (document.body.scrollTop) { return document.body.scrollTop; }
    return 0;
  }

  function getElementY(document, element) {
    var y = element.offsetTop;
    var node = element;
    while (node.offsetParent && node.offsetParent !== document.body) {
      node = node.offsetParent;
      y += node.offsetTop;
    }
    return y;
  }

  this.scrollDown = function (startY, stopY, speed, distance) {

    var timer = 0;

    var step = Math.round(distance / 25);
    var leapY = startY + step;

    for (var i = startY; i < stopY; i += step) {
      setTimeout('window.scrollTo(0, ' + leapY + ')', timer * speed);
      leapY += step;
      if (leapY > stopY){ leapY = stopY; }
      timer++;
    }
  };

  this.scrollUp = function (startY, stopY, speed, distance) {

    var timer = 0;

    var step = Math.round(distance / 25);
    var leapY = startY - step;

    for (var i = startY; i > stopY; i -= step) {
      setTimeout('window.scrollTo(0, ' + leapY + ')', timer * speed);
      leapY -= step;
      if (leapY < stopY) { leapY = stopY; }
      timer++;
    }
  };

  this.scrollToTop = function (stopY) {
    scrollTo(0, stopY);
  };

  this.scrollTo = function (elementId, speed) {
    // This scrolling function
    // is from http://www.itnewb.com/tutorial/Creating-the-Smooth-Scroll-Effect-with-JavaScript

    var element = document.getElementById(elementId);

    if (element) {
      var startY = getCurrentPagePosition(window, document);
      var stopY = getElementY(document, element);

      var distance = stopY > startY ? stopY - startY : startY - stopY;

      if (distance < 100) {
        this.scrollToTop(stopY);

      } else {

        var defaultSpeed = Math.round(distance / 100);
        speed = speed || (defaultSpeed > 20 ? 20 : defaultSpeed);

        if (stopY > startY) {
          this.scrollDown(startY, stopY, speed, distance);
        } else {
          this.scrollUp(startY, stopY, speed, distance);
        }
      }

    }

  };

});