make emitter

src/utils/events.ts

@@ -0,0 +1,33 @@
+export type EventMap = Record<string, any>;
+type EventKey<T extends EventMap> = string & keyof T;
+type EventReceiver<T> = (params: T) => void;
+
+export interface Emitter<T extends EventMap> {
+  on<K extends EventKey<T>>(eventName: K, fn: EventReceiver<T[K]>): void;
+  off<K extends EventKey<T>>(eventName: K, fn: EventReceiver<T[K]>): void;
+  emit<K extends EventKey<T>>(eventName: K, params: T[K]): void;
+}
+
+export interface Listener<T extends EventMap> {
+  on<K extends EventKey<T>>(eventName: K, fn: EventReceiver<T[K]>): void;
+}
+
+export function makeEmitter<T extends EventMap>(): Emitter<T> {
+  const listeners: Partial<
+    Record<EventKey<T>, ((...params: any[]) => void)[]>
+  > = {};
+
+  return {
+    on(eventName, fn) {
+      if (!listeners[eventName]) listeners[eventName] = [];
+      listeners[eventName]?.push(fn);
+    },
+    off(eventName, fn) {
+      listeners[eventName] =
+        listeners[eventName]?.filter((v) => v !== fn) ?? [];
+    },
+    emit(eventName, params) {
+      (listeners[eventName] ?? []).forEach((fn) => fn(params));
+    },
+  };
+}