setup events

src/events.js

@@ -0,0 +1,42 @@
+class EventEmitter {
+
+    constructor() {
+        this.eventListenersMap = new Map();
+    }
+
+    on(event, callback) {
+
+        // create list of listeners for event if it doesn't exist
+        if(!this.eventListenersMap.has(event)){
+            this.eventListenersMap.set(event, []);
+        }
+
+        // add listener for event
+        this.eventListenersMap.get(event).push(callback);
+
+    }
+
+    off(event, callback) {
+
+        // remove callback from listeners for this event
+        if(this.eventListenersMap.has(event)){
+            const callbacks = this.eventListenersMap.get(event).filter(cb => cb !== callback);
+            this.eventListenersMap.set(event, callbacks);
+        }
+
+    }
+
+    emit(event, ...data) {
+
+        // invoke each listener for this event
+        if(this.eventListenersMap.has(event)){
+            for(const eventListener of this.eventListenersMap.get(event)){
+                setTimeout(() => eventListener(...data), 0);
+            }
+        }
+
+    }
+
+}
+
+export default EventEmitter;