Merged #1361

CHANGELOG.md

@@ -156,6 +156,7 @@ All the random notes that should make up a nice changelog:
 * Dropped already deprecated toplevel `map` function
 * Killed the already deprecated modifiers `asFlat` etc. If you war still using this, see the MobX 2 -> 3 migration notes.
 * `autorun` now accepts a scheduler function to allow improved performance for tasks such as rendering to canvas
+* Observable maps now fully implement the map interface. See [#1361](https://github.com/mobxjs/mobx/pull/1361) by [Marc Fallows](https://github.com/marcfallows)
 
 # 3.6.1
 

src/types/observablemap.ts

@@ -10,7 +10,8 @@ import {
     invariant,
     isES6Map,
     getMapLikeKeys,
-    fail
+    fail,
+    addHiddenFinalProp
 } from "../utils/utils"
 import {
     IInterceptable,
@@ -78,7 +79,8 @@ export class ObservableMap<K, V>
     interceptors
     changeListeners
     dehancer: any;
-    [Symbol.iterator]
+    [Symbol.iterator];
+    [Symbol.toStringTag]
 
     constructor(
         initialData?: IObservableMapInitialValues<K, V>,
@@ -374,6 +376,12 @@ declareIterator(ObservableMap.prototype, function() {
     return this.entries()
 })
 
+addHiddenFinalProp(
+    ObservableMap.prototype,
+    typeof Symbol !== "undefined" ? Symbol.toStringTag : "@@toStringTag" as any,
+    "Map"
+)
+
 /* 'var' fixes small-build issue */
 export var isObservableMap = createInstanceofPredicate("ObservableMap", ObservableMap) as (
     thing: any

test/base/map.js

@@ -678,3 +678,9 @@ test("maps.values, keys and maps.entries are iterables", () => {
     expect(Array.from(x.values())).toEqual([1, 2])
     expect(Array.from(x.keys())).toEqual(["x", "y"])
 })
+
+test("toStringTag", () => {
+    const x = mobx.observable.map({ x: 1, y: 2 })
+    expect(x[Symbol.toStringTag]).toBe("Map")
+    expect(Object.prototype.toString.call(x)).toBe("[object Map]")
+})

test/base/typescript-tests.ts

@@ -1499,3 +1499,9 @@ test.skip("actions are reassignable", () => {
     a.m2 = () => {}
     expect(isAction(a.m2)).toBe(true)
 })
+
+test("map should structurally match ES6 Map", () => {
+    // Including this line strictly for type checking.
+    const m: Map<string, number> = mobx.observable.map({ a: 1, b: 2 })
+    expect(true).toBe(true)
+})