added new events class

src/core/Events.js

@@ -0,0 +1,83 @@
+/**
+* See [Demo.js](https://github.com/liabru/matter-js/blob/master/demo/js/Demo.js) 
+* and [DemoMobile.js](https://github.com/liabru/matter-js/blob/master/demo/js/DemoMobile.js) for usage examples.
+*
+* @class Events
+*/
+
+var Events = {};
+
+(function() {
+
+    /**
+     * Subscribes a callback function to the given object's eventName
+     * @method on
+     * @param {} object
+     * @param {string} eventNames
+     * @param {function} callback
+     */
+    Events.on = function(object, eventNames, callback) {
+        var names = eventNames.split(' '),
+            name;
+
+        for (var i = 0; i < names.length; i++) {
+            name = names[i];
+            object.events = object.events || {};
+            object.events[name] = object.events[name] || [];
+            object.events[name].push(callback);
+        }
+    };
+
+    /**
+     * Fires all the callbacks subscribed to the given object's eventName, in the order they subscribed, if any
+     * @method fire
+     * @param {} object
+     * @param {string} eventNames
+     * @param {} event
+     */
+    Events.trigger = function(object, eventNames, event) {
+        var names,
+            name,
+            callbacks,
+            eventClone;
+
+        if (object.events) {
+            event = event || {};
+            names = eventNames.split(' ');
+
+            for (var i = 0; i < names.length; i++) {
+                name = names[i];
+
+                if (name in object.events) {
+                    callbacks = object.events[name];
+                    eventClone = Common.clone(event, false);
+                    eventClone.name = name;
+                    eventClone.source = object;
+
+                    for (var j = 0; j < callbacks.length; j++) {
+                        callbacks[j].apply(object, [eventClone]);
+                    }
+                }
+            }
+        }
+    };
+
+    /**
+     * Clears all callbacks for the given event names if supplied, otherwise all events
+     * @method clear
+     * @param {} object
+     * @param {string} eventNames
+     */
+    Events.clear = function(object, eventNames) {
+        if (!eventNames) {
+            object.events = {};
+            return;
+        }
+
+        var names = eventNames.split(' ');
+        for (var i = 0; i < names.length; i++) {
+            object.events[names[i]] = [];
+        }
+    };
+
+})();