Implemented Symbol.toStringTag for observable arrays, fixes #1490

mobxjs · Apr 16, 2018 · b21b5e2 · b21b5e2
1 parent 394c418
commit b21b5e2
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Showing 3 changed files with 16 additions and 1 deletion.
diff --git a/src/types/observablearray.ts b/src/types/observablearray.ts
@@ -602,6 +602,14 @@ Object.defineProperty(ObservableArray.prototype, "length", {
     }
 })
 
+if (typeof Symbol !== "undefined" && Symbol.toStringTag) {
+    addHiddenProp(
+        ObservableArray.prototype,
+        typeof Symbol !== "undefined" ? Symbol.toStringTag : "@@toStringTag" as any,
+        "Array"
+    )
+}
+
 // Internet Explorer on desktop doesn't support this.....
 // So, let's don't do this to avoid different semantics
 // See #1395

diff --git a/src/utils/utils.ts b/src/utils/utils.ts
@@ -96,7 +96,7 @@ export function makeNonEnumerable(object: any, propNames: string[]) {
     }
 }
 
-export function addHiddenProp(object: any, propName: string, value: any) {
+export function addHiddenProp(object: any, propName: PropertyKey, value: any) {
     Object.defineProperty(object, propName, {
         enumerable: false,
         writable: true,

diff --git a/test/base/array.js b/test/base/array.js
@@ -504,3 +504,10 @@ test("array is spreadable, #1395", () => {
     const y = mobx.observable([])
     expect([5, ...y]).toEqual([5])
 })
+
+test("array supports toStringTag, #1490", () => {
+    // N.B. on old environments this requires polyfils for these symbols *and* Object.prototype.toString.
+    // core-js provides both
+    const a = mobx.observable([])
+    expect(Object.prototype.toString.call(a)).toBe("[object Array]")
+})