Variable event names

index.d.ts

@@ -1,44 +1,59 @@
 export type Arguments<T> = [T] extends [(...args: infer U) => any]
-  ? U
-  : [T] extends [void] ? [] : [T]
+	? U
+	: [T] extends [void]
+	? []
+	: [T];
+
+export type EventFunction = (...args: any[]) => void;
+export type EmitterEvents = EmitterEvent<string, EventFunction>;
+export type EmitterEvent<Name extends string, Func extends EventFunction> = {
+	name: Name;
+	args: Arguments<Func>;
+};
 
 /**
  * Type-safe event emitter.
  *
  * Use it like this:
  *
- * interface MyEvents {
- *   error: (error: Error) => void
- *   message: (from: string, content: string) => void
- * }
+ * type DynamicEvents =
+ * | EmitterEvent<'ping', () => void>
+ * | EmitterEvent<'message', (from: string, content: string) => void>
+ * | EmmiterEvents<'error': (error: Error) => void>
+ * | EmitterEvent<`foo:${string}`, (size: number, strict: boolean) => void>
+ * | EmitterEvent<`bar:${string}`, (force: boolean) => void>;
  *
- * const myEmitter = new EventEmitter() as TypedEmitter<MyEvents>
+ * const myEmitter = new EventEmitter() as TypedEmitter<DynamicEvents>
  *
  * myEmitter.on("message", (from, content) => {
  *   // ...
  * })
  *
  * myEmitter.emit("error", "x")  // <- Will catch this type error
+ *
+ * myEmitter.emit("foo:1", 2, false) // dynamic/variable event names work
+ * myEmitter.emit(`foo:${'456'}`, 2, false)
+ *
  */
-interface TypedEventEmitter<Events> {
-  addListener<E extends keyof Events> (event: E, listener: Events[E]): this
-  on<E extends keyof Events> (event: E, listener: Events[E]): this
-  once<E extends keyof Events> (event: E, listener: Events[E]): this
-  prependListener<E extends keyof Events> (event: E, listener: Events[E]): this
-  prependOnceListener<E extends keyof Events> (event: E, listener: Events[E]): this
+export interface TypedEventEmitter<Events extends EmitterEvents> {
+	addListener<E extends keyof Events>(event: E, listener: Events[E]): this;
+	on<E extends keyof Events>(event: E, listener: Events[E]): this;
+	once<E extends keyof Events>(event: E, listener: Events[E]): this;
+	prependListener<E extends keyof Events>(event: E, listener: Events[E]): this;
+	prependOnceListener<E extends keyof Events>(event: E, listener: Events[E]): this;
 
-  off<E extends keyof Events>(event: E, listener: Events[E]): this
-  removeAllListeners<E extends keyof Events> (event?: E): this
-  removeListener<E extends keyof Events> (event: E, listener: Events[E]): this
+	off<E extends keyof Events>(event: E, listener: Events[E]): this;
+	removeAllListeners<E extends keyof Events>(event?: E): this;
+	removeListener<E extends keyof Events>(event: E, listener: Events[E]): this;
 
-  emit<E extends keyof Events> (event: E, ...args: Arguments<Events[E]>): boolean
-  eventNames (): (keyof Events | string | symbol)[]
-  rawListeners<E extends keyof Events> (event: E): Function[]
-  listeners<E extends keyof Events> (event: E): Function[]
-  listenerCount<E extends keyof Events> (event: E): number
+	emit<E extends Events>(name: E['name'], ...args: E['args']): boolean;
+	eventNames(): (keyof Events | string | symbol)[];
+	rawListeners<E extends keyof Events>(event: E): Function[];
+	listeners<E extends keyof Events>(event: E): Function[];
+	listenerCount<E extends keyof Events>(event: E): number;
 
-  getMaxListeners (): number
-  setMaxListeners (maxListeners: number): this
+	getMaxListeners(): number;
+	setMaxListeners(maxListeners: number): this;
 }
 
-export default TypedEventEmitter
+export default TypedEventEmitter;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "typed-emitter",
-  "version": "1.3.1",
+  "version": "1.3.4",
   "license": "MIT",
   "description": "Strictly typed event emitter interface for TypeScript 3.",
   "author": "Andy Wermke (https://github.com/andywer)",