added unit testing, and started implementing unit tests...phew

node_modules/nise/lib/event/event-target.js

@@ -0,0 +1,107 @@
+"use strict";
+
+function flattenOptions(options) {
+    if (options !== Object(options)) {
+        return {
+            capture: Boolean(options),
+            once: false,
+            passive: false
+        };
+    }
+    return {
+        capture: Boolean(options.capture),
+        once: Boolean(options.once),
+        passive: Boolean(options.passive)
+    };
+}
+function not(fn) {
+    return function () {
+        return !fn.apply(this, arguments);
+    };
+}
+function hasListenerFilter(listener, capture) {
+    return function (listenerSpec) {
+        return listenerSpec.capture === capture
+            && listenerSpec.listener === listener;
+    };
+}
+
+var EventTarget = {
+    // https://dom.spec.whatwg.org/#dom-eventtarget-addeventlistener
+    addEventListener: function addEventListener(event, listener, providedOptions) {
+        // 3. Let capture, passive, and once be the result of flattening more options.
+        // Flatten property before executing step 2,
+        // feture detection is usually based on registering handler with options object,
+        // that has getter defined
+        // addEventListener("load", () => {}, {
+        //    get once() { supportsOnce = true; }
+        // });
+        var options = flattenOptions(providedOptions);
+
+        // 2. If callback is null, then return.
+        if (listener == null) {
+            return;
+        }
+
+        this.eventListeners = this.eventListeners || {};
+        this.eventListeners[event] = this.eventListeners[event] || [];
+
+        // 4. If context object’s associated list of event listener
+        //    does not contain an event listener whose type is type,
+        //    callback is callback, and capture is capture, then append
+        //    a new event listener to it, whose type is type, callback is
+        //    callback, capture is capture, passive is passive, and once is once.
+        if (!this.eventListeners[event].some(hasListenerFilter(listener, options.capture))) {
+            this.eventListeners[event].push({
+                listener: listener,
+                capture: options.capture,
+                once: options.once
+            });
+        }
+    },
+
+    // https://dom.spec.whatwg.org/#dom-eventtarget-removeeventlistener
+    removeEventListener: function removeEventListener(event, listener, providedOptions) {
+        if (!this.eventListeners || !this.eventListeners[event]) {
+            return;
+        }
+
+        // 2. Let capture be the result of flattening options.
+        var options = flattenOptions(providedOptions);
+
+        // 3. If there is an event listener in the associated list of
+        //    event listeners whose type is type, callback is callback,
+        //    and capture is capture, then set that event listener’s
+        //    removed to true and remove it from the associated list of event listeners.
+        this.eventListeners[event] = this.eventListeners[event]
+            .filter(not(hasListenerFilter(listener, options.capture)));
+    },
+
+    dispatchEvent: function dispatchEvent(event) {
+        if (!this.eventListeners || !this.eventListeners[event.type]) {
+            return Boolean(event.defaultPrevented);
+        }
+
+        var self = this;
+        var type = event.type;
+        var listeners = self.eventListeners[type];
+
+        // Remove listeners, that should be dispatched once
+        // before running dispatch loop to avoid nested dispatch issues
+        self.eventListeners[type] = listeners.filter(function (listenerSpec) {
+            return !listenerSpec.once;
+        });
+        listeners.forEach(function (listenerSpec) {
+            var listener = listenerSpec.listener;
+            if (typeof listener === "function") {
+                listener.call(self, event);
+            } else {
+                listener.handleEvent(event);
+            }
+        });
+
+        return Boolean(event.defaultPrevented);
+    }
+};
+
+module.exports = EventTarget;