Fix ES6 Map/Set checks for cross-window scripts (#3893)

.changeset/fresh-apricots-heal.md

@@ -0,0 +1,5 @@
+---
+"mobx": patch
+---
+
+Fix ES6 Map/Set checks for cross-window scripts

packages/mobx/src/types/observablemap.ts

@@ -16,6 +16,7 @@ import {
  hasListeners,
  interceptChange,
  isES6Map,
+ isPlainES6Map,
  isPlainObject,
  isSpyEnabled,
  makeIterable,
@@ -351,7 +352,7 @@ export class ObservableMap<K = any, V = any>
  } else if (Array.isArray(other)) {
  other.forEach(([key, value]) => this.set(key, value))
  } else if (isES6Map(other)) {
- if (other.constructor !== Map) {
+ if (!isPlainES6Map(other)) {
  die(19, other)
  }
  other.forEach((value, key) => this.set(key, value))

packages/mobx/src/utils/utils.ts

@@ -141,11 +141,18 @@ export function createInstanceofPredicate<T>(
 }
 
 export function isES6Map(thing: any): thing is Map<any, any> {
- return thing instanceof Map
+ return thing != null && Object.prototype.toString.call(thing) === "[object Map]"
+}
+
+export function isPlainES6Map(thing: Map<any, any>): boolean {
+ const mapProto = Object.getPrototypeOf(thing)
+ const objectProto = Object.getPrototypeOf(mapProto)
+ const nullProto = Object.getPrototypeOf(objectProto)
+ return nullProto === null
 }
 
 export function isES6Set(thing: any): thing is Set<any> {
- return thing instanceof Set
+ return thing != null && Object.prototype.toString.call(thing) === "[object Set]"
 }
 
 const hasGetOwnPropertySymbols = typeof Object.getOwnPropertySymbols !== "undefined"