From 6d5c1a4a70870e8ab5a36f9590875460a10c67b0 Mon Sep 17 00:00:00 2001
From: cha0s <git@cha0s.io>
Date: Mon, 18 Jan 2021 21:02:52 -0600
Subject: [PATCH] chore: error

---
 packages/core/src/event-emitter.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/packages/core/src/event-emitter.js b/packages/core/src/event-emitter.js
index d0f0045..795b54b 100644
--- a/packages/core/src/event-emitter.js
+++ b/packages/core/src/event-emitter.js
@@ -107,6 +107,9 @@ export default function EventEmitterMixin(Superclass) {
     }
 
     onSingleEvent(type, fn, that, once) {
+      if ('function' !== typeof fn) {
+        throw new TypeError('EventEmitter::onSingleEvent() requires function listener');
+      }
       const listener = createListener(fn, that, type, once);
       if (!(type in this.$$events)) {
         this.$$events[type] = [];