diff --git a/dom/chrome-webidl/IteratorResult.webidl b/dom/chrome-webidl/IteratorResult.webidl
new file mode 100644
index 000000000000..1fdd26810e07
--- /dev/null
+++ b/dom/chrome-webidl/IteratorResult.webidl
@@ -0,0 +1,14 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+/**
+ * A dictionary which represents the result of a call to a next() method on a
+ * JS iterator object.
+ */
+dictionary IteratorResult {
+  required boolean done;
+  any value;
+};
diff --git a/dom/chrome-webidl/moz.build b/dom/chrome-webidl/moz.build
index cfd9e800e19a..f7830ca97787 100644
--- a/dom/chrome-webidl/moz.build
+++ b/dom/chrome-webidl/moz.build
@@ -34,6 +34,7 @@ WEBIDL_FILES = [
     'DominatorTree.webidl',
     'HeapSnapshot.webidl',
     'InspectorUtils.webidl',
+    'IteratorResult.webidl',
     'MatchGlob.webidl',
     'MatchPattern.webidl',
     'MessageManager.webidl',
diff --git a/netwerk/test/httpserver/httpd.js b/netwerk/test/httpserver/httpd.js
index 9e5a19073557..e5115d44cad3 100644
--- a/netwerk/test/httpserver/httpd.js
+++ b/netwerk/test/httpserver/httpd.js
@@ -5130,6 +5130,9 @@ nsSimpleEnumerator.prototype =
 
     return this._items[this._nextIndex++];
   },
+  [Symbol.iterator]() {
+    return this._items.values();
+  },
   QueryInterface: function(aIID)
   {
     if (Ci.nsISimpleEnumerator.equals(aIID) ||
diff --git a/testing/specialpowers/content/MockFilePicker.jsm b/testing/specialpowers/content/MockFilePicker.jsm
index a44338848630..30ac42144bbc 100644
--- a/testing/specialpowers/content/MockFilePicker.jsm
+++ b/testing/specialpowers/content/MockFilePicker.jsm
@@ -214,12 +214,15 @@ MockFilePickerInstance.prototype = {
     return {
       index: 0,
       QueryInterface: ChromeUtils.generateQI([Ci.nsISimpleEnumerator]),
+      [Symbol.iterator]() {
+        return Array.from(MockFilePicker.returnData, d => d.nsIFile).values();
+      },
       hasMoreElements() {
         return this.index < MockFilePicker.returnData.length;
       },
       getNext() {
         if (!MockFilePicker.returnData[this.index].nsIFile) {
-          return null;
+          throw Components.Exception("", Cr.NS_ERROR_FAILURE);
         }
         return MockFilePicker.returnData[this.index++].nsIFile;
       }
diff --git a/xpcom/ds/nsISimpleEnumerator.idl b/xpcom/ds/nsISimpleEnumerator.idl
index cbb0cd2000c6..ccad2a16722e 100644
--- a/xpcom/ds/nsISimpleEnumerator.idl
+++ b/xpcom/ds/nsISimpleEnumerator.idl
@@ -14,8 +14,38 @@
  * @version 1.0
  */
 
+/**
+ * A wrapper for an nsISimpleEnumerator instance which implements the
+ * JavaScript iteration protocol.
+ */
+[scriptable, uuid(4432e8ae-d4d3-42a6-a4d1-829f1c29512b)]
+interface nsIJSEnumerator : nsISupports {
+  [symbol]
+  nsIJSEnumerator iterator();
+
+  [implicit_jscontext]
+  jsval next();
+};
+
+[scriptable, uuid(796f340d-0a2a-490b-9c60-640765e99782)]
+interface nsISimpleEnumeratorBase : nsISupports {
+  /**
+   * Returns a JavaScript iterator for all remaining entries in the enumerator.
+   * Each entry is queried only to nsISupports.
+   */
+  [symbol]
+  nsIJSEnumerator iterator();
+
+  /**
+   * Returns JavaScript iterator for all remaining entries in the enumerator.
+   * Each entry is queried only to the supplied interface. If any element
+   * fails to query to that interface, the error is propagated to the caller.
+   */
+  nsIJSEnumerator entries(in nsIIDRef aIface);
+};
+
 [scriptable, uuid(D1899240-F9D2-11D2-BDD6-000064657374)]
-interface nsISimpleEnumerator : nsISupports {
+interface nsISimpleEnumerator : nsISimpleEnumeratorBase {
   /**
    * Called to determine whether or not the enumerator has
    * any elements that can be returned via getNext(). This method
@@ -27,7 +57,7 @@ interface nsISimpleEnumerator : nsISupports {
    * @see getNext()
    * @return true if there are remaining elements in the enumerator.
    *         false if there are no more elements in the enumerator.
-   */                                            
+   */
   boolean hasMoreElements();
 
   /**
diff --git a/xpcom/ds/nsSimpleEnumerator.cpp b/xpcom/ds/nsSimpleEnumerator.cpp
index 8c28c780a1bf..b540ab63e64c 100644
--- a/xpcom/ds/nsSimpleEnumerator.cpp
+++ b/xpcom/ds/nsSimpleEnumerator.cpp
@@ -6,4 +6,82 @@
 
 #include "nsSimpleEnumerator.h"
 
-NS_IMPL_ISUPPORTS(nsSimpleEnumerator, nsISimpleEnumerator)
+#include "mozilla/dom/IteratorResultBinding.h"
+#include "mozilla/dom/RootedDictionary.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/ResultExtensions.h"
+#include "nsContentUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+namespace {
+
+class JSEnumerator final : public nsIJSEnumerator
+{
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIJSENUMERATOR
+
+  explicit JSEnumerator(nsISimpleEnumerator* aEnumerator, const nsID& aIID)
+    : mEnumerator(aEnumerator)
+    , mIID(aIID)
+  {}
+
+private:
+  ~JSEnumerator() = default;
+
+  nsCOMPtr<nsISimpleEnumerator> mEnumerator;
+  const nsID mIID;
+};
+
+} // anonymous namespace
+
+nsresult
+JSEnumerator::Iterator(nsIJSEnumerator** aResult)
+{
+  RefPtr<JSEnumerator> result(this);
+  result.forget(aResult);
+  return NS_OK;
+}
+
+nsresult
+JSEnumerator::Next(JSContext* aCx, JS::MutableHandleValue aResult)
+{
+  RootedDictionary<IteratorResult> result(aCx);
+
+  nsCOMPtr<nsISupports> elem;
+  if (NS_FAILED(mEnumerator->GetNext(getter_AddRefs(elem)))) {
+    result.mDone = true;
+  } else {
+    result.mDone = false;
+
+    JS::RootedValue value(aCx);
+    MOZ_TRY(nsContentUtils::WrapNative(aCx, elem, &mIID, &value));
+    result.mValue = value;
+  }
+
+  if (!ToJSValue(aCx, result, aResult)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(JSEnumerator, nsIJSEnumerator)
+
+nsresult
+nsSimpleEnumerator::Iterator(nsIJSEnumerator **aResult)
+{
+  auto result = MakeRefPtr<JSEnumerator>(this, NS_GET_IID(nsISupports));
+  result.forget(aResult);
+  return NS_OK;
+}
+
+nsresult
+nsSimpleEnumerator::Entries(const nsIID& aIface, nsIJSEnumerator **aResult)
+{
+  auto result = MakeRefPtr<JSEnumerator>(this, aIface);
+  result.forget(aResult);
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(nsSimpleEnumerator, nsISimpleEnumerator, nsISimpleEnumeratorBase)
diff --git a/xpcom/ds/nsSimpleEnumerator.h b/xpcom/ds/nsSimpleEnumerator.h
index 9c474e32f316..afb195b4c7cf 100644
--- a/xpcom/ds/nsSimpleEnumerator.h
+++ b/xpcom/ds/nsSimpleEnumerator.h
@@ -12,6 +12,7 @@
 class nsSimpleEnumerator : public nsISimpleEnumerator
 {
   NS_DECL_ISUPPORTS
+  NS_DECL_NSISIMPLEENUMERATORBASE
 
 protected:
   virtual ~nsSimpleEnumerator() = default;
diff --git a/xpcom/io/nsLocalFileUnix.cpp b/xpcom/io/nsLocalFileUnix.cpp
index b814cc3181fa..b59860286c96 100644
--- a/xpcom/io/nsLocalFileUnix.cpp
+++ b/xpcom/io/nsLocalFileUnix.cpp
@@ -108,6 +108,8 @@ public:
 
   NS_IMETHOD Init(nsLocalFile* aParent, bool aIgnored);
 
+  NS_FORWARD_NSISIMPLEENUMERATORBASE(nsSimpleEnumerator::)
+
 private:
   ~nsDirEnumeratorUnix() override;
 
diff --git a/xpcom/io/nsLocalFileWin.cpp b/xpcom/io/nsLocalFileWin.cpp
index 1dab317d9abb..e2d334a37341 100644
--- a/xpcom/io/nsLocalFileWin.cpp
+++ b/xpcom/io/nsLocalFileWin.cpp
@@ -238,6 +238,7 @@ public:
   nsDriveEnumerator();
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_NSISIMPLEENUMERATOR
+  NS_FORWARD_NSISIMPLEENUMERATORBASE(nsSimpleEnumerator::)
   nsresult Init();
 
   NS_IMETHOD GetNextFile(nsIFile** aResult) override
@@ -694,6 +695,8 @@ private:
 public:
   NS_DECL_ISUPPORTS_INHERITED
 
+  NS_FORWARD_NSISIMPLEENUMERATORBASE(nsSimpleEnumerator::)
+
   nsDirEnumerator() : mDir(nullptr)
   {
   }