diff --git a/scrollMonitor.js b/scrollMonitor.js
index fc1fce9..772d2bd 100755
--- a/scrollMonitor.js
+++ b/scrollMonitor.js
@@ -1,412 +1,428 @@
-(function( factory ) {
-	if (typeof define !== 'undefined' && define.amd) {
-		define(['jquery'], factory);
-	} else if (typeof module !== 'undefined' && module.exports) {
-		var jQuery = require('jquery');
-		module.exports = factory( $ );
-	} else {
-		window.scrollMonitor = factory( $ );
-	}
-})(function( $ ) {
-
-	var exports = {};
-
-	var VISIBILITYCHANGE = 'visibilityChange';
-	var ENTERVIEWPORT = 'enterViewport';
-	var FULLYENTERVIEWPORT = 'fullyEnterViewport';
-	var EXITVIEWPORT = 'exitViewport';
-	var PARTIALLYEXITVIEWPORT = 'partiallyExitViewport';
-	var LOCATIONCHANGE = 'locationChange';
-	var STATECHANGE = 'stateChange';
-
-	var eventTypes = [
-		VISIBILITYCHANGE,
-		ENTERVIEWPORT,
-		FULLYENTERVIEWPORT,
-		EXITVIEWPORT,
-		PARTIALLYEXITVIEWPORT,
-		LOCATIONCHANGE,
-		STATECHANGE
-	];
-
-	var defaultOffsets = {top: 0, bottom: 0};
-
-
-	function ScrollMonitor( $container ) {
-		var self = this;
-
-		this.watchers = [];
-
-		this.$container = $container;
-		if (this.$container[0] === window) {
-			this.$document = $(document);
-		}
-
-		this.viewportTop = null;
-		this.viewportBottom = null;
-		this.documentHeight = null;
-		this.viewportHeight = this.$container.height();
-
-		function scrollMonitorListener(event) {
-			self.latestEvent = event;
-			self.calculateViewport();
-			self.updateAndTriggerWatchers();
-		}
-
-		var recalculateAndTriggerTimer;
-		function debouncedRecalcuateAndTrigger() {
-			clearTimeout(recalculateAndTriggerTimer);
-			recalculateAndTriggerTimer = setTimeout( $.proxy(self.recalculateWatchLocationsAndTrigger, self), 100 );
-		}
-
-		this.$container.on('scroll', scrollMonitorListener);
-		if (this.$document) {
-			this.$container.on('resize', debouncedRecalcuateAndTrigger);
-		}
-
-		this.calculateViewport();
-	}
-
-	ScrollMonitor.prototype = {
-		calculateViewport: function() {
-			var calculateViewportI;
-			this.viewportTop = this.$container.scrollTop();
-			this.viewportBottom = this.viewportTop + this.viewportHeight;
-			this.documentHeight = this.$document ? this.$document.height() : this.$container.prop("scrollHeight");
-			if (this.documentHeight !== this.previousDocumentHeight) {
-				calculateViewportI = this.watchers.length;
-				while( calculateViewportI-- ) {
-					this.watchers[calculateViewportI].recalculateLocation();
-				}
-				this.previousDocumentHeight = this.documentHeight;
-			}
-		},
-		recalculateWatchLocationsAndTrigger: function() {
-			this.viewportHeight = this.$container.height();
-			this.calculateViewport();
-			this.updateAndTriggerWatchers();
-		},
-		updateAndTriggerWatchers: function() {
-			var updateAndTriggerWatchersI;
-			// update all watchers then trigger the events so one can rely on another being up to date.
-			updateAndTriggerWatchersI = this.watchers.length;
-			while( updateAndTriggerWatchersI-- ) {
-				this.watchers[updateAndTriggerWatchersI].update();
-			}
-
-			updateAndTriggerWatchersI = this.watchers.length;
-			while( updateAndTriggerWatchersI-- ) {
-				this.watchers[updateAndTriggerWatchersI].triggerCallbacks();
-			}
-		},
-		create: function( element, options ) {
-			if (typeof element === 'string') {
-				element = $(element)[0];
-			}
-			if (element instanceof $) {
-				element = element[0];
-			}
-			options.scrollMonitor = this;
-			var watcher = new ElementWatcher( element, options );
-			this.watchers.push(watcher);
-			watcher.update();
-			return watcher;
-		},
-		update: function() {
-			this.latestEvent = null;
-			this.calculateViewport();
-			this.updateAndTriggerWatchers();
-		},
-		recalculateLocations: function() {
-			this.documentHeight = 0;
-			this.update();
-		}
-	};
-
-	function ElementWatcher( watchItem, options ) {
-		var self = this,
-			offsets = options.offsets;
-
-		this.watchItem = watchItem;
-		this.scrollMonitor = options.scrollMonitor;
-		this.checkVisibility = options.checkVisibility;
-
-		if (!offsets) {
-			this.offsets = defaultOffsets;
-		} else if (offsets === +offsets) {
-			this.offsets = {top: offsets, bottom: offsets};
-		} else {
-			this.offsets = $.extend({}, defaultOffsets, offsets);
-		}
-
-		this.callbacks = {}; // {callback: function, isOne: true }
-
-		eventTypes.forEach(function(type) {
-			self.callbacks[type] = [];
-		});
-
-		this.locked = false;
-
-		var wasInViewport;
-		var wasFullyInViewport;
-		var wasAboveViewport;
-		var wasBelowViewport;
-
-		var listenerToTriggerListI;
-		var listener;
-		function triggerCallbackArray( listeners ) {
-			if (listeners.length === 0) {
-				return;
-			}
-			listenerToTriggerListI = listeners.length;
-			while( listenerToTriggerListI-- ) {
-				listener = listeners[listenerToTriggerListI];
-				listener.callback.call( self, self.scrollMonitor.latestEvent );
-				if (listener.isOne) {
-					listeners.splice(listenerToTriggerListI, 1);
-				}
-			}
-		}
-
-		this.triggerCallbacks = function triggerCallbacks() {
-
-			if (this.isInViewport && !wasInViewport) {
-				triggerCallbackArray( this.callbacks[ENTERVIEWPORT] );
-			}
-			if (this.isFullyInViewport && !wasFullyInViewport) {
-				triggerCallbackArray( this.callbacks[FULLYENTERVIEWPORT] );
-			}
-
-
-			if (this.isAboveViewport !== wasAboveViewport &&
-				this.isBelowViewport !== wasBelowViewport) {
-
-				triggerCallbackArray( this.callbacks[VISIBILITYCHANGE] );
-
-				// if you skip completely past this element
-				if (!wasFullyInViewport && !this.isFullyInViewport) {
-					triggerCallbackArray( this.callbacks[FULLYENTERVIEWPORT] );
-					triggerCallbackArray( this.callbacks[PARTIALLYEXITVIEWPORT] );
-				}
-				if (!wasInViewport && !this.isInViewport) {
-					triggerCallbackArray( this.callbacks[ENTERVIEWPORT] );
-					triggerCallbackArray( this.callbacks[EXITVIEWPORT] );
-				}
-			}
-
-			if (!this.isFullyInViewport && wasFullyInViewport) {
-				triggerCallbackArray( this.callbacks[PARTIALLYEXITVIEWPORT] );
-			}
-			if (!this.isInViewport && wasInViewport) {
-				triggerCallbackArray( this.callbacks[EXITVIEWPORT] );
-			}
-			if (this.isInViewport !== wasInViewport) {
-				triggerCallbackArray( this.callbacks[VISIBILITYCHANGE] );
-			}
-			switch( true ) {
-				case wasInViewport !== this.isInViewport:
-				case wasFullyInViewport !== this.isFullyInViewport:
-				case wasAboveViewport !== this.isAboveViewport:
-				case wasBelowViewport !== this.isBelowViewport:
-					triggerCallbackArray( this.callbacks[STATECHANGE] );
-			}
-
-			wasInViewport = this.isInViewport;
-			wasFullyInViewport = this.isFullyInViewport;
-			wasAboveViewport = this.isAboveViewport;
-			wasBelowViewport = this.isBelowViewport;
-
-		};
-
-		this.recalculateLocation = function() {
-			if (this.locked) {
-				return;
-			}
-			var previousTop = this.top;
-			var previousBottom = this.bottom;
-			if (this.watchItem.nodeName) { // a dom element
-				var cachedDisplay = this.watchItem.style.display;
-				if (cachedDisplay === 'none') {
-					this.watchItem.style.display = '';
-				}
-
-				if (!this.$watchItem) {
-					this.$watchItem = $(this.watchItem);
-				}
-				var elementLocation = this.scrollMonitor.$document ? this.$watchItem.offset() : this.$watchItem.position();
-				this.top = elementLocation.top;
-				this.bottom = elementLocation.top + this.watchItem.offsetHeight;
-
-				if (cachedDisplay === 'none') {
-					this.watchItem.style.display = cachedDisplay;
-				}
-
-			} else if (this.watchItem === +this.watchItem) { // number
-				if (this.watchItem > 0) {
-					this.top = this.bottom = this.watchItem;
-				} else {
-					this.top = this.bottom = this.scrollMonitor.documentHeight - this.watchItem;
-				}
-
-			} else { // an object with a top and bottom property
-				this.top = this.watchItem.top;
-				this.bottom = this.watchItem.bottom;
-			}
-
-			this.top -= this.offsets.top;
-			this.bottom += this.offsets.bottom;
-			this.height = this.bottom - this.top;
-
-			if ( (previousTop !== undefined || previousBottom !== undefined) && (this.top !== previousTop || this.bottom !== previousBottom) ) {
-				triggerCallbackArray( this.callbacks[LOCATIONCHANGE] );
-			}
-		};
-
-
-		this.recalculateLocation();
-
-		this.update();
-
-		wasInViewport = this.isInViewport;
-		wasFullyInViewport = this.isFullyInViewport;
-		wasAboveViewport = this.isAboveViewport;
-		wasBelowViewport = this.isBelowViewport;
-	}
-
-
-
-
-	ElementWatcher.prototype = {
-		on: function( event, callback, isOne ) {
-
-			// trigger the event if it applies to the element right now.
-			switch( true ) {
-				case event === VISIBILITYCHANGE && !this.isInViewport && this.isAboveViewport:
-				case event === ENTERVIEWPORT && this.isInViewport:
-				case event === FULLYENTERVIEWPORT && this.isFullyInViewport:
-				case event === EXITVIEWPORT && this.isAboveViewport && !this.isInViewport:
-				case event === PARTIALLYEXITVIEWPORT && this.isAboveViewport:
-					callback();
-					if (isOne) {
-						return;
-					}
-			}
-
-			if (this.callbacks[event]) {
-				this.callbacks[event].push({callback: callback, isOne: isOne});
-			} else {
-				throw new Error('Tried to add a scroll monitor listener of type '+event+'. Your options are: '+eventTypes.join(', '));
-			}
-		},
-		off: function( event, callback ) {
-			if (this.callbacks[event]) {
-				for (var i = 0, item; item = this.callbacks[event][i]; i++) {
-					if (item.callback === callback) {
-						this.callbacks[event].splice(i, 1);
-						break;
-					}
-				}
-			} else {
-				throw new Error('Tried to remove a scroll monitor listener of type '+event+'. Your options are: '+eventTypes.join(', '));
-			}
-		},
-		one: function( event, callback ) {
-			this.on( event, callback, true);
-		},
-		recalculateSize: function() {
-			this.height = this.watchItem.offsetHeight + this.offsets.top + this.offsets.bottom;
-			this.bottom = this.top + this.height;
-		},
-		update: function() {
-			var thisRect, isVisible = $(this.watchItem).is(":visible");
-			if(isWindowScrollMonitor(this.scrollMonitor.$container)){
-				thisRect = this;
-			} else {
-				thisRect = this.watchItem.getBoundingClientRect();
-			}
-			if(this.checkVisibility && !isVisible){
-				this.isAboveViewport = false;
-				this.isBelowViewport = false;
-				this.isInViewport = false;
-				this.isFullyInViewport = false;
-			} else {
-				this.isAboveViewport = thisRect.top < this.scrollMonitor.viewportTop;
-				this.isBelowViewport = thisRect.bottom > this.scrollMonitor.viewportBottom;
-				this.isInViewport = (thisRect.top <= this.scrollMonitor.viewportBottom && thisRect.bottom >= this.scrollMonitor.viewportTop);
-				this.isFullyInViewport = (thisRect.top >= this.scrollMonitor.viewportTop && thisRect.bottom <= this.scrollMonitor.viewportBottom) ||
-				(thisRect.isAboveViewport && thisRect.isBelowViewport);
-			}
-		},
-		destroy: function() {
-			var index = this.scrollMonitor.watchers.indexOf(this),
-				self  = this;
-			this.scrollMonitor.watchers.splice(index, 1);
-			eventTypes.forEach(function(type) {
-				self.callbacks[type].length = 0;
-			});
-		},
-		// prevent recalculating the element location
-		lock: function() {
-			this.locked = true;
-		},
-		unlock: function() {
-			this.locked = false;
-		}
-	};
-
-	eventTypes.forEach(function( type ) {
-		ElementWatcher.prototype[type] = function( callback, isOne) {
-			this.on.call(this, type, callback, isOne);
-		};
-	});
-
-
-	var windowScrollMonitor = new ScrollMonitor( $(window) );
-
-	function isWindowScrollMonitor( $container ) {
-		if (!$container) {
-			return true;
-		} else if ($container[0] == window || $container[0] == document.body) {
-			return true;
-		} else {
-			return false;
-		}
-	}
-
-	exports.getInstance = function( $container ) {
-		if (isWindowScrollMonitor($container)) {
-			return windowScrollMonitor;
-		} else {
-			return $container.data('scrollMonitor');
-		}
-	};
-	exports.beget = exports.create = function( element, options ) {
-		var $container = options.$container,
-			scrollMonitor = isWindowScrollMonitor($container) ? windowScrollMonitor : $container.data('scrollMonitor');
-
-		if ($container && !scrollMonitor) {
-			scrollMonitor = new ScrollMonitor($container);
-			$container.data('scrollMonitor', scrollMonitor);
-		}
-		return scrollMonitor.create(element, options);
-	};
-	exports.update = function( $container ) {
-		this.getInstance($container).update();
-	};
-	exports.recalculateLocations = function( $container ) {
-		this.getInstance($container).recalculateLocations();
-	};
-	exports.viewportTop = function( $container ) {
-		return this.getInstance($container).viewportTop;
-	};
-	exports.viewportBottom = function( $container ) {
-		return this.getInstance($container).viewportBottom;
-	};
-	exports.documentHeight = function( $container ) {
-		return this.getInstance($container).documentHeight;
-	};
-	exports.viewportHeight = function( $container ) {
-		return this.getInstance($container).viewportHeight;
-	};
-	return exports;
-});
\ No newline at end of file
+(function (factory) {
+    if (typeof define !== 'undefined' && define.amd) {
+        define(['jquery'], factory);
+    } else if (typeof module !== 'undefined' && module.exports) {
+        var jQuery = require('jquery');
+        module.exports = factory($);
+    } else {
+        window.scrollMonitor = factory($);
+    }
+})(function ($) {
+
+    var exports = {};
+
+    var VISIBILITYCHANGE = 'visibilityChange';
+    var ENTERVIEWPORT = 'enterViewport';
+    var FULLYENTERVIEWPORT = 'fullyEnterViewport';
+    var EXITVIEWPORT = 'exitViewport';
+    var PARTIALLYEXITVIEWPORT = 'partiallyExitViewport';
+    var LOCATIONCHANGE = 'locationChange';
+    var STATECHANGE = 'stateChange';
+
+    var eventTypes = [
+        VISIBILITYCHANGE,
+        ENTERVIEWPORT,
+        FULLYENTERVIEWPORT,
+        EXITVIEWPORT,
+        PARTIALLYEXITVIEWPORT,
+        LOCATIONCHANGE,
+        STATECHANGE
+    ];
+
+    var defaultOffsets = {
+        top: 0,
+        bottom: 0
+    };
+
+
+    function ScrollMonitor($container) {
+        var self = this;
+
+        this.watchers = [];
+
+        this.$container = $container;
+        if (this.$container[0] === window) {
+            this.$document = $(document);
+        }
+
+        this.viewportTop = null;
+        this.viewportBottom = null;
+        this.documentHeight = null;
+        this.viewportHeight = this.$container.height();
+
+        function scrollMonitorListener(event) {
+            self.latestEvent = event;
+            self.calculateViewport();
+            self.updateAndTriggerWatchers();
+        }
+
+        var recalculateAndTriggerTimer;
+
+        function debouncedRecalcuateAndTrigger() {
+            clearTimeout(recalculateAndTriggerTimer);
+            recalculateAndTriggerTimer = setTimeout($.proxy(self.recalculateWatchLocationsAndTrigger, self), 100);
+        }
+
+        this.$container.on('scroll', scrollMonitorListener);
+        if (this.$document) {
+            this.$container.on('resize', debouncedRecalcuateAndTrigger);
+        }
+
+        this.calculateViewport();
+    }
+
+    ScrollMonitor.prototype = {
+        calculateViewport: function () {
+            var calculateViewportI;
+            this.viewportTop = this.$container.scrollTop();
+            this.viewportBottom = this.viewportTop + this.viewportHeight;
+            this.documentHeight = this.$document ? this.$document.height() : this.$container.prop('scrollHeight');
+            if (this.documentHeight !== this.previousDocumentHeight) {
+                calculateViewportI = this.watchers.length;
+                while (calculateViewportI--) {
+                    this.watchers[calculateViewportI].recalculateLocation();
+                }
+                this.previousDocumentHeight = this.documentHeight;
+            }
+        },
+        recalculateWatchLocationsAndTrigger: function () {
+            this.viewportHeight = this.$container.height();
+            this.calculateViewport();
+            this.updateAndTriggerWatchers();
+        },
+        updateAndTriggerWatchers: function () {
+            var updateAndTriggerWatchersI;
+            // update all watchers then trigger the events so one can rely on another being up to date.
+            updateAndTriggerWatchersI = this.watchers.length;
+            while (updateAndTriggerWatchersI--) {
+                this.watchers[updateAndTriggerWatchersI].update();
+            }
+
+            updateAndTriggerWatchersI = this.watchers.length;
+            while (updateAndTriggerWatchersI--) {
+                this.watchers[updateAndTriggerWatchersI].triggerCallbacks();
+            }
+        },
+        create: function (element, options) {
+            if (typeof element === 'string') {
+                element = $(element)[0];
+            }
+            if (element instanceof $) {
+                element = element[0];
+            }
+            options.scrollMonitor = this;
+            var watcher = new ElementWatcher(element, options);
+            this.watchers.push(watcher);
+            watcher.update();
+            return watcher;
+        },
+        update: function () {
+            this.latestEvent = null;
+            this.calculateViewport();
+            this.updateAndTriggerWatchers();
+        },
+        recalculateLocations: function () {
+            this.documentHeight = 0;
+            this.update();
+        }
+    };
+
+    function ElementWatcher(watchItem, options) {
+        var self = this;
+        var offsets = options.offsets;
+
+        this.watchItem = watchItem;
+        this.scrollMonitor = options.scrollMonitor;
+        this.checkVisibility = options.checkVisibility;
+
+        if (!offsets) {
+            this.offsets = defaultOffsets;
+        } else if (offsets === +offsets) {
+            this.offsets = {
+                top: offsets,
+                bottom: offsets
+            };
+        } else {
+            this.offsets = $.extend({}, defaultOffsets, offsets);
+        }
+
+        this.callbacks = {}; // {callback: function, isOne: true }
+
+        eventTypes.forEach(function (type) {
+            self.callbacks[type] = [];
+        });
+
+        this.locked = false;
+
+        var wasInViewport;
+        var wasFullyInViewport;
+        var wasAboveViewport;
+        var wasBelowViewport;
+
+        var listenerToTriggerListI;
+        var listener;
+
+        function triggerCallbackArray(listeners) {
+            if (listeners.length === 0) {
+                return;
+            }
+            listenerToTriggerListI = listeners.length;
+            while (listenerToTriggerListI--) {
+                listener = listeners[listenerToTriggerListI];
+                listener.callback.call(self, self.scrollMonitor.latestEvent);
+                if (listener.isOne) {
+                    listeners.splice(listenerToTriggerListI, 1);
+                }
+            }
+        }
+
+        this.triggerCallbacks = function triggerCallbacks() {
+
+            if (this.isInViewport && !wasInViewport) {
+                triggerCallbackArray(this.callbacks[ENTERVIEWPORT]);
+            }
+            if (this.isFullyInViewport && !wasFullyInViewport) {
+                triggerCallbackArray(this.callbacks[FULLYENTERVIEWPORT]);
+            }
+
+
+            if (this.isAboveViewport !== wasAboveViewport &&
+                this.isBelowViewport !== wasBelowViewport) {
+
+                triggerCallbackArray(this.callbacks[VISIBILITYCHANGE]);
+
+                // if you skip completely past this element
+                if (!wasFullyInViewport && !this.isFullyInViewport) {
+                    triggerCallbackArray(this.callbacks[FULLYENTERVIEWPORT]);
+                    triggerCallbackArray(this.callbacks[PARTIALLYEXITVIEWPORT]);
+                }
+                if (!wasInViewport && !this.isInViewport) {
+                    triggerCallbackArray(this.callbacks[ENTERVIEWPORT]);
+                    triggerCallbackArray(this.callbacks[EXITVIEWPORT]);
+                }
+            }
+
+            if (!this.isFullyInViewport && wasFullyInViewport) {
+                triggerCallbackArray(this.callbacks[PARTIALLYEXITVIEWPORT]);
+            }
+            if (!this.isInViewport && wasInViewport) {
+                triggerCallbackArray(this.callbacks[EXITVIEWPORT]);
+            }
+            if (this.isInViewport !== wasInViewport) {
+                triggerCallbackArray(this.callbacks[VISIBILITYCHANGE]);
+            }
+            switch (true) {
+                case wasInViewport !== this.isInViewport:
+                case wasFullyInViewport !== this.isFullyInViewport:
+                case wasAboveViewport !== this.isAboveViewport:
+                case wasBelowViewport !== this.isBelowViewport:
+                    triggerCallbackArray(this.callbacks[STATECHANGE]);
+            }
+
+            wasInViewport = this.isInViewport;
+            wasFullyInViewport = this.isFullyInViewport;
+            wasAboveViewport = this.isAboveViewport;
+            wasBelowViewport = this.isBelowViewport;
+
+        };
+
+        this.recalculateLocation = function () {
+            if (this.locked) {
+                return;
+            }
+            var previousTop = this.top;
+            var previousBottom = this.bottom;
+            if (this.watchItem.nodeName) { // a dom element
+                var cachedDisplay = this.watchItem.style.display;
+                if (cachedDisplay === 'none') {
+                    this.watchItem.style.display = '';
+                }
+
+                if (!this.$watchItem) {
+                    this.$watchItem = $(this.watchItem);
+                }
+                var elementLocation = this.scrollMonitor.$document ? this.$watchItem.offset() : this.$watchItem.position();
+                this.top = elementLocation.top;
+                this.bottom = elementLocation.top + this.watchItem.offsetHeight;
+
+                if (cachedDisplay === 'none') {
+                    this.watchItem.style.display = cachedDisplay;
+                }
+
+            } else if (this.watchItem === +this.watchItem) { // number
+                if (this.watchItem > 0) {
+                    this.top = this.bottom = this.watchItem;
+                } else {
+                    this.top = this.bottom = this.scrollMonitor.documentHeight - this.watchItem;
+                }
+
+            } else { // an object with a top and bottom property
+                this.top = this.watchItem.top;
+                this.bottom = this.watchItem.bottom;
+            }
+
+            this.top -= this.offsets.top;
+            this.bottom += this.offsets.bottom;
+            this.height = this.bottom - this.top;
+
+            if ((previousTop !== undefined || previousBottom !== undefined) && (this.top !== previousTop || this.bottom !== previousBottom)) {
+                triggerCallbackArray(this.callbacks[LOCATIONCHANGE]);
+            }
+        };
+
+
+        this.recalculateLocation();
+
+        this.update();
+
+        wasInViewport = this.isInViewport;
+        wasFullyInViewport = this.isFullyInViewport;
+        wasAboveViewport = this.isAboveViewport;
+        wasBelowViewport = this.isBelowViewport;
+    }
+
+    ElementWatcher.prototype = {
+        on: function (event, callback, isOne) {
+
+            // trigger the event if it applies to the element right now.
+            switch (true) {
+                case event === VISIBILITYCHANGE && !this.isInViewport && this.isAboveViewport:
+                case event === ENTERVIEWPORT && this.isInViewport:
+                case event === FULLYENTERVIEWPORT && this.isFullyInViewport:
+                case event === EXITVIEWPORT && this.isAboveViewport && !this.isInViewport:
+                case event === PARTIALLYEXITVIEWPORT && this.isAboveViewport:
+                    callback();
+                    if (isOne) {
+                        return;
+                    }
+            }
+
+            if (this.callbacks[event]) {
+                this.callbacks[event].push({
+                    callback: callback,
+                    isOne: isOne
+                });
+            } else {
+                throw new Error('Tried to add a scroll monitor listener of type ' + event + '. Your options are: ' + eventTypes.join(', '));
+            }
+        },
+        off: function (event, callback) {
+            if (this.callbacks[event]) {
+                for (var i = 0, item; item = this.callbacks[event][i]; i++) {
+                    if (item.callback === callback) {
+                        this.callbacks[event].splice(i, 1);
+                        break;
+                    }
+                }
+            } else {
+                throw new Error('Tried to remove a scroll monitor listener of type ' + event + '. Your options are: ' + eventTypes.join(', '));
+            }
+        },
+        one: function (event, callback) {
+            this.on(event, callback, true);
+        },
+        recalculateSize: function () {
+            this.height = this.watchItem.offsetHeight + this.offsets.top + this.offsets.bottom;
+            this.bottom = this.top + this.height;
+        },
+        update: function () {
+            var thisRect;
+            var isVisible = $(this.watchItem).is(':visible');
+
+            if (isWindowScrollMonitor(this.scrollMonitor.$container)) {
+                thisRect = this;
+            } else {
+                //GWAR-1011 Wrap in try/catch to prevent IE11 from choking
+                try {
+                    thisRect = this.watchItem.getBoundingClientRect();
+                } catch (e) {
+                    //do nothing
+                }
+            }
+            if (this.checkVisibility && !isVisible) {
+                this.isAboveViewport = false;
+                this.isBelowViewport = false;
+                this.isInViewport = false;
+                this.isFullyInViewport = false;
+            } else {
+                this.isAboveViewport = thisRect.top < this.scrollMonitor.viewportTop;
+                this.isBelowViewport = thisRect.bottom > this.scrollMonitor.viewportBottom;
+                this.isInViewport = (thisRect.top <= this.scrollMonitor.viewportBottom && thisRect.bottom >= this.scrollMonitor.viewportTop);
+                this.isFullyInViewport = (thisRect.top >= this.scrollMonitor.viewportTop && thisRect.bottom <= this.scrollMonitor.viewportBottom) ||
+                    (thisRect.isAboveViewport && thisRect.isBelowViewport);
+            }
+        },
+        destroy: function () {
+            var index = this.scrollMonitor.watchers.indexOf(this);
+            var self = this;
+            this.scrollMonitor.watchers.splice(index, 1);
+            eventTypes.forEach(function (type) {
+                self.callbacks[type].length = 0;
+            });
+        },
+        // prevent recalculating the element location
+        lock: function () {
+            this.locked = true;
+        },
+        unlock: function () {
+            this.locked = false;
+        }
+    };
+
+    eventTypes.forEach(function (type) {
+        ElementWatcher.prototype[type] = function (callback, isOne) {
+            this.on.call(this, type, callback, isOne);
+        };
+    });
+
+
+    var windowScrollMonitor = new ScrollMonitor($(window));
+
+    function isWindowScrollMonitor($container) {
+        if (!$container) {
+            return true;
+        } else if ($container[0] === window || $container[0] === document.body) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    exports.getInstance = function ($container) {
+        if (isWindowScrollMonitor($container)) {
+            return windowScrollMonitor;
+        } else {
+            return $container.data('scrollMonitor');
+        }
+    };
+    exports.beget = exports.create = function (element, options) {
+        var $container = options.$container;
+        var scrollMonitor = isWindowScrollMonitor($container) ? windowScrollMonitor : $container.data('scrollMonitor');
+
+        if ($container && !scrollMonitor) {
+            scrollMonitor = new ScrollMonitor($container);
+            $container.data('scrollMonitor', scrollMonitor);
+        }
+        return scrollMonitor.create(element, options);
+    };
+    exports.update = function ($container) {
+        this.getInstance($container).update();
+    };
+    exports.recalculateLocations = function ($container) {
+        this.getInstance($container).recalculateLocations();
+    };
+    exports.viewportTop = function ($container) {
+        return this.getInstance($container).viewportTop;
+    };
+    exports.viewportBottom = function ($container) {
+        return this.getInstance($container).viewportBottom;
+    };
+    exports.documentHeight = function ($container) {
+        return this.getInstance($container).documentHeight;
+    };
+    exports.viewportHeight = function ($container) {
+        return this.getInstance($container).viewportHeight;
+    };
+    return exports;
+});
+