From a3ec6b1f095bffe4875d7e688f7f30f22530c45e Mon Sep 17 00:00:00 2001
From: "wayne.zhou" <wayne.zhou@ringcentral.com>
Date: Sun, 11 Aug 2019 16:08:41 +0800
Subject: [PATCH] fix: onBecome(Un)Observed didn't trigger when using number as
 key of observable map.

---
 CHANGELOG.md                 |  2 ++
 src/api/become-observed.ts   |  4 ++--
 test/base/become-observed.js | 13 +++++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 test/base/become-observed.js

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f647858bf..e6ebd5f4b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,8 @@
 # 5.13.1 / 4.13.1
 
 * Don't use `global` and `self` keywords unless defined. Fixes [#2070](https://github.com/mobxjs/mobx/issues/2070).
+* onBecome(Un)Observed didn't trigger when using number as key of observable map. Fixes [#2067](https://github.com/mobxjs/mobx/issues/2067).
+
 
 # 5.13.0 / 4.13.0
 
diff --git a/src/api/become-observed.ts b/src/api/become-observed.ts
index 968006fa4..aff3306cc 100644
--- a/src/api/become-observed.ts
+++ b/src/api/become-observed.ts
@@ -47,8 +47,8 @@ export function onBecomeUnobserved(thing, arg2, arg3?): Lambda {
 
 function interceptHook(hook: "onBecomeObserved" | "onBecomeUnobserved", thing, arg2, arg3) {
     const atom: IObservable =
-        typeof arg2 === "string" ? getAtom(thing, arg2) : (getAtom(thing) as any)
-    const cb = typeof arg2 === "string" ? arg3 : arg2
+        typeof arg3 === "function" ? getAtom(thing, arg2) : (getAtom(thing) as any)
+    const cb = typeof arg3 === "function" ? arg3 : arg2
     const listenersKey = `${hook}Listeners` as
         | "onBecomeObservedListeners"
         | "onBecomeUnobservedListeners"
diff --git a/test/base/become-observed.js b/test/base/become-observed.js
new file mode 100644
index 000000000..a282fe22d
--- /dev/null
+++ b/test/base/become-observed.js
@@ -0,0 +1,13 @@
+import { autorun, onBecomeObserved, observable } from "../../src/mobx"
+
+describe("become-observed", () => {
+    it("work on map with number as key", () => {
+        const oMap = observable.map()
+        const key = 1
+        oMap.set(key, observable.box("value"))
+        const cb = jest.fn()
+        onBecomeObserved(oMap, key, cb)
+        autorun(() => oMap.get(key))
+        expect(cb).toBeCalled()
+    })
+})