base con front

public/lib/bus.js

@@ -0,0 +1,17 @@
+const listeners = new Map();
+
+export function on(event, fn) {
+  const arr = listeners.get(event) || [];
+  arr.push(fn);
+  listeners.set(event, arr);
+  return () => off(event, fn);
+}
+
+export function off(event, fn) {
+  const arr = listeners.get(event) || [];
+  listeners.set(event, arr.filter(x => x !== fn));
+}
+
+export function emit(event, payload) {
+  (listeners.get(event) || []).forEach(fn => fn(payload));
+}