1 files changed, 75 insertions, 0 deletions
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..f0a2ebb
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,75 @@
+type EventType = string | symbol;
+
+// An event handler can take an optional event argument
+// and should not return a value
+type Handler = (event?: any) => void;
+type WildcardHandler= (type: EventType, event?: any) => void
+
+// An array of all currently registered event handlers for a type
+type EventHandlerList = Array<Handler>;
+type WildCardEventHandlerList = Array<WildcardHandler>;
+
+// A map of event types and their corresponding event handlers.
+type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;
+
+export interface Emitter {
+	on(type: EventType, handler: Handler): void;
+	on(type: "*", handler: WildcardHandler): void;
+
+	off(type: EventType, handler: Handler): void;
+	off(type: "*", handler: WildcardHandler): void;
+
+	emit<T = any>(type: EventType, event?: T): void;
+	emit(type: "*", event?: any): void;
+}
+
+/** Mitt: Tiny (~200b) functional event emitter / pubsub.
+ *  @name mitt
+ *  @returns {Mitt}
+ */
+export default function mitt(all: EventHandlerMap): Emitter {
+	all = all || new Map();
+
+	return {
+		/**
+		 * Register an event handler for the given type.
+		 *
+		 * @param {string|symbol} type Type of event to listen for, or `"*"` for all events
+		 * @param {Function} handler Function to call in response to given event
+		 * @memberOf mitt
+		 */
+		on(type: EventType, handler: Handler) {
+			const handlers = (all.get(type) || []);
+			handlers.push(handler);
+			all.set(type, handlers);
+		},
+
+		/**
+		 * Remove an event handler for the given type.
+		 *
+		 * @param {string|symbol} type Type of event to unregister `handler` from, or `"*"`
+		 * @param {Function} handler Handler function to remove
+		 * @memberOf mitt
+		 */
+		off(type: EventType, handler: Handler) {
+			if (all.has(type)) {
+				all.get(type).splice(all.get(type).indexOf(handler) >>> 0, 1);
+			}
+		},
+
+		/**
+		 * Invoke all handlers for the given type.
+		 * If present, `"*"` handlers are invoked after type-matched handlers.
+		 *
+		 * Note: Manually firing "*" handlers is not supported.
+		 *
+		 * @param {string|symbol} type The event type to invoke
+		 * @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler
+		 * @memberOf mitt
+		 */
+		emit(type: EventType, evt: any) {
+			((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });
+			((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });
+		}
+	};
+}