scrollEnd.js

/*
 * All code Copyright Benjamin Best 2013 unless otherwise referenced.  Licensed
 * under the MIT License, see the LICENSE file included in this repository for
 * the full terms.
 */
ScrollEnd = (function () {
  var ScrollEnd;

  function getScrollTop() {
      // from http://stackoverflow.com/questions/871399/cross-browser-method-for-detecting-the-scrolltop-of-the-browser-window
        if (typeof pageYOffset != 'undefined') {
          return pageYOffset;
        } else {
          var B = document.body;
          var D = document.documentElement;
          D = (D.clientHeight) ? D : B;
          return D.scrollTop;
        }
  };

  ScrollEnd = function (options) {
    var checkInterval = (options && options.checkInterval) || 100,
    scrolling = false,
    lastScrollPosition = getScrollTop(),
    i = 0,
    that = this;

    this.subscribers = [];

    setInterval(function() {
      var scrollPosition = getScrollTop();
      if (scrolling && scrollPosition === lastScrollPosition) {
        // we have stopped scrolling
        scrolling = false;
        for (i = 0; i < that.subscribers.length; i++) {
          that.subscribers[i](scrollPosition);
        }
      } else if (!scrolling && scrollPosition !== lastScrollPosition) {
        // we have started scrolling
        scrolling = true;
      }
      lastScrollPosition = scrollPosition;
    }, checkInterval);
  };

  // subscribe to the ScrollEnd event
  ScrollEnd.prototype.subscribe = function (func) {
    this.subscribers.push(func);
  };

  // unsusbscribe from the ScrollEnd event
  ScrollEnd.prototype.unsubscribe = function (func) {
    var idx = this.subscribers.indexOf(func);
    if (idx >= 0) {
      this.subscribers.splice(idx, 1);
    }
  };

  // Aliases for subscribe and unsubscribe
  ScrollEnd.prototype.sub = ScrollEnd.prototype.subscribe;
  ScrollEnd.prototype.unsub = ScrollEnd.prototype.unsubscribe;

  return ScrollEnd;
})();