flow like the river

VISUALIZACION/node_modules/ngraph.events/index.js

@@ -0,0 +1,88 @@
+module.exports = function eventify(subject) {
+  validateSubject(subject);
+
+  var eventsStorage = createEventsStorage(subject);
+  subject.on = eventsStorage.on;
+  subject.off = eventsStorage.off;
+  subject.fire = eventsStorage.fire;
+  return subject;
+};
+
+function createEventsStorage(subject) {
+  // Store all event listeners to this hash. Key is event name, value is array
+  // of callback records.
+  //
+  // A callback record consists of callback function and its optional context:
+  // { 'eventName' => [{callback: function, ctx: object}] }
+  var registeredEvents = Object.create(null);
+
+  return {
+    on: function (eventName, callback, ctx) {
+      if (typeof callback !== 'function') {
+        throw new Error('callback is expected to be a function');
+      }
+      var handlers = registeredEvents[eventName];
+      if (!handlers) {
+        handlers = registeredEvents[eventName] = [];
+      }
+      handlers.push({callback: callback, ctx: ctx});
+
+      return subject;
+    },
+
+    off: function (eventName, callback) {
+      var wantToRemoveAll = (typeof eventName === 'undefined');
+      if (wantToRemoveAll) {
+        // Killing old events storage should be enough in this case:
+        registeredEvents = Object.create(null);
+        return subject;
+      }
+
+      if (registeredEvents[eventName]) {
+        var deleteAllCallbacksForEvent = (typeof callback !== 'function');
+        if (deleteAllCallbacksForEvent) {
+          delete registeredEvents[eventName];
+        } else {
+          var callbacks = registeredEvents[eventName];
+          for (var i = 0; i < callbacks.length; ++i) {
+            if (callbacks[i].callback === callback) {
+              callbacks.splice(i, 1);
+            }
+          }
+        }
+      }
+
+      return subject;
+    },
+
+    fire: function (eventName) {
+      var callbacks = registeredEvents[eventName];
+      if (!callbacks) {
+        return subject;
+      }
+
+      var fireArguments;
+      if (arguments.length > 1) {
+        fireArguments = Array.prototype.splice.call(arguments, 1);
+      }
+      for(var i = 0; i < callbacks.length; ++i) {
+        var callbackInfo = callbacks[i];
+        callbackInfo.callback.apply(callbackInfo.ctx, fireArguments);
+      }
+
+      return subject;
+    }
+  };
+}
+
+function validateSubject(subject) {
+  if (!subject) {
+    throw new Error('Eventify cannot use falsy object as events subject');
+  }
+  var reservedWords = ['on', 'fire', 'off'];
+  for (var i = 0; i < reservedWords.length; ++i) {
+    if (subject.hasOwnProperty(reservedWords[i])) {
+      throw new Error("Subject cannot be eventified, since it already has property '" + reservedWords[i] + "'");
+    }
+  }
+}