diff --git a/packages/react-dom/src/__tests__/ReactTestUtils-test.js b/packages/react-dom/src/__tests__/ReactTestUtils-test.js
index d926e85641..a69c046565 100644
--- a/packages/react-dom/src/__tests__/ReactTestUtils-test.js
+++ b/packages/react-dom/src/__tests__/ReactTestUtils-test.js
@@ -15,6 +15,8 @@ import * as ReactDOM from 'react-dom';
 import * as ReactDOMServer from 'react-dom/server';
 import * as ReactTestUtils from 'react-dom/test-utils';
 
+const ReactFeatureFlags = require('shared/ReactFeatureFlags');
+
 function getTestDocument(markup) {
   const doc = document.implementation.createHTMLDocument('');
   doc.open();
@@ -31,25 +33,97 @@ describe('ReactTestUtils', () => {
     expect(Object.keys(ReactTestUtils.Simulate).sort()).toMatchSnapshot();
   });
 
-  it('SimulateNative should have locally attached media events', () => {
-    expect(Object.keys(ReactTestUtils.SimulateNative).sort()).toMatchSnapshot();
-  });
+  if (!ReactFeatureFlags.enableModernEventSystem) {
+    // SimulateNative API has been removed in the modern event system
+    it('SimulateNative should have locally attached media events', () => {
+      expect(Object.keys(ReactTestUtils.SimulateNative).sort()).toEqual([
+        'abort',
+        'animationEnd',
+        'animationIteration',
+        'animationStart',
+        'blur',
+        'canPlay',
+        'canPlayThrough',
+        'cancel',
+        'change',
+        'click',
+        'close',
+        'compositionEnd',
+        'compositionStart',
+        'compositionUpdate',
+        'contextMenu',
+        'copy',
+        'cut',
+        'doubleClick',
+        'drag',
+        'dragEnd',
+        'dragEnter',
+        'dragExit',
+        'dragLeave',
+        'dragOver',
+        'dragStart',
+        'drop',
+        'durationChange',
+        'emptied',
+        'encrypted',
+        'ended',
+        'error',
+        'focus',
+        'input',
+        'keyDown',
+        'keyPress',
+        'keyUp',
+        'load',
+        'loadStart',
+        'loadedData',
+        'loadedMetadata',
+        'mouseDown',
+        'mouseMove',
+        'mouseOut',
+        'mouseOver',
+        'mouseUp',
+        'paste',
+        'pause',
+        'play',
+        'playing',
+        'progress',
+        'rateChange',
+        'scroll',
+        'seeked',
+        'seeking',
+        'selectionChange',
+        'stalled',
+        'suspend',
+        'textInput',
+        'timeUpdate',
+        'toggle',
+        'touchCancel',
+        'touchEnd',
+        'touchMove',
+        'touchStart',
+        'transitionEnd',
+        'volumeChange',
+        'waiting',
+        'wheel',
+      ]);
+    });
 
-  it('SimulateNative should warn about deprecation', () => {
-    const container = document.createElement('div');
-    const node = ReactDOM.render(<div />, container);
-    expect(() =>
-      ReactTestUtils.SimulateNative.click(node),
-    ).toWarnDev(
-      'ReactTestUtils.SimulateNative is an undocumented API that does not match ' +
-        'how the browser dispatches events, and will be removed in a future major ' +
-        'version of React. If you rely on it for testing, consider attaching the root ' +
-        'DOM container to the document during the test, and then dispatching native browser ' +
-        'events by calling `node.dispatchEvent()` on the DOM nodes. Make sure to set ' +
-        'the `bubbles` flag to `true` when creating the native browser event.',
-      {withoutStack: true},
-    );
-  });
+    it('SimulateNative should warn about deprecation', () => {
+      const container = document.createElement('div');
+      const node = ReactDOM.render(<div />, container);
+      expect(() =>
+        ReactTestUtils.SimulateNative.click(node),
+      ).toWarnDev(
+        'ReactTestUtils.SimulateNative is an undocumented API that does not match ' +
+          'how the browser dispatches events, and will be removed in a future major ' +
+          'version of React. If you rely on it for testing, consider attaching the root ' +
+          'DOM container to the document during the test, and then dispatching native browser ' +
+          'events by calling `node.dispatchEvent()` on the DOM nodes. Make sure to set ' +
+          'the `bubbles` flag to `true` when creating the native browser event.',
+        {withoutStack: true},
+      );
+    });
+  }
 
   it('gives Jest mocks a passthrough implementation with mockComponent()', () => {
     class MockedComponent extends React.Component {
diff --git a/packages/react-dom/src/__tests__/__snapshots__/ReactTestUtils-test.js.snap b/packages/react-dom/src/__tests__/__snapshots__/ReactTestUtils-test.js.snap
index 14f2058dd8..9f37f55219 100644
--- a/packages/react-dom/src/__tests__/__snapshots__/ReactTestUtils-test.js.snap
+++ b/packages/react-dom/src/__tests__/__snapshots__/ReactTestUtils-test.js.snap
@@ -88,76 +88,3 @@ Array [
   "wheel",
 ]
 `;
-
-exports[`ReactTestUtils SimulateNative should have locally attached media events 1`] = `
-Array [
-  "abort",
-  "animationEnd",
-  "animationIteration",
-  "animationStart",
-  "blur",
-  "canPlay",
-  "canPlayThrough",
-  "cancel",
-  "change",
-  "click",
-  "close",
-  "compositionEnd",
-  "compositionStart",
-  "compositionUpdate",
-  "contextMenu",
-  "copy",
-  "cut",
-  "doubleClick",
-  "drag",
-  "dragEnd",
-  "dragEnter",
-  "dragExit",
-  "dragLeave",
-  "dragOver",
-  "dragStart",
-  "drop",
-  "durationChange",
-  "emptied",
-  "encrypted",
-  "ended",
-  "error",
-  "focus",
-  "input",
-  "keyDown",
-  "keyPress",
-  "keyUp",
-  "load",
-  "loadStart",
-  "loadedData",
-  "loadedMetadata",
-  "mouseDown",
-  "mouseMove",
-  "mouseOut",
-  "mouseOver",
-  "mouseUp",
-  "paste",
-  "pause",
-  "play",
-  "playing",
-  "progress",
-  "rateChange",
-  "scroll",
-  "seeked",
-  "seeking",
-  "selectionChange",
-  "stalled",
-  "suspend",
-  "textInput",
-  "timeUpdate",
-  "toggle",
-  "touchCancel",
-  "touchEnd",
-  "touchMove",
-  "touchStart",
-  "transitionEnd",
-  "volumeChange",
-  "waiting",
-  "wheel",
-]
-`;
diff --git a/packages/react-dom/src/events/DOMModernPluginEventSystem.js b/packages/react-dom/src/events/DOMModernPluginEventSystem.js
index 2642d9f349..3bc74b86d9 100644
--- a/packages/react-dom/src/events/DOMModernPluginEventSystem.js
+++ b/packages/react-dom/src/events/DOMModernPluginEventSystem.js
@@ -218,7 +218,7 @@ function dispatchEventsForPlugins(
   eventSystemFlags: EventSystemFlags,
   nativeEvent: AnyNativeEvent,
   targetInst: null | Fiber,
-  targetContainer: null | EventTarget,
+  targetContainer: EventTarget,
 ): void {
   const nativeEventTarget = getEventTarget(nativeEvent);
   const syntheticEvents: Array<ReactSyntheticEvent> = [];
@@ -395,90 +395,85 @@ export function dispatchEventForPluginEventSystem(
   eventSystemFlags: EventSystemFlags,
   nativeEvent: AnyNativeEvent,
   targetInst: null | Fiber,
-  targetContainer: null | EventTarget,
+  targetContainer: EventTarget,
 ): void {
   let ancestorInst = targetInst;
-  if (targetContainer !== null) {
-    if (eventSystemFlags & IS_TARGET_PHASE_ONLY) {
-      // For TargetEvent nodes (i.e. document, window)
-      ancestorInst = null;
-    } else {
-      const targetContainerNode = ((targetContainer: any): Node);
+  if (eventSystemFlags & IS_TARGET_PHASE_ONLY) {
+    // For TargetEvent nodes (i.e. document, window)
+    ancestorInst = null;
+  } else {
+    const targetContainerNode = ((targetContainer: any): Node);
 
-      // If we are using the legacy FB support flag, we
-      // defer the event to the null with a one
-      // time event listener so we can defer the event.
-      if (
-        enableLegacyFBSupport &&
-        // We do not want to defer if the event system has already been
-        // set to LEGACY_FB_SUPPORT. LEGACY_FB_SUPPORT only gets set when
-        // we call willDeferLaterForLegacyFBSupport, thus not bailing out
-        // will result in endless cycles like an infinite loop.
-        (eventSystemFlags & LEGACY_FB_SUPPORT) === 0 &&
-        // We also don't want to defer during event replaying.
-        (eventSystemFlags & IS_REPLAYED) === 0 &&
-        // We don't want to apply the legacy FB support for the useEvent API.
-        (eventSystemFlags & USE_EVENT_SYSTEM) === 0 &&
-        willDeferLaterForLegacyFBSupport(topLevelType, targetContainer)
-      ) {
-        return;
-      }
-      if (targetInst !== null) {
-        // The below logic attempts to work out if we need to change
-        // the target fiber to a different ancestor. We had similar logic
-        // in the legacy event system, except the big difference between
-        // systems is that the modern event system now has an event listener
-        // attached to each React Root and React Portal Root. Together,
-        // the DOM nodes representing these roots are the "rootContainer".
-        // To figure out which ancestor instance we should use, we traverse
-        // up the fiber tree from the target instance and attempt to find
-        // root boundaries that match that of our current "rootContainer".
-        // If we find that "rootContainer", we find the parent fiber
-        // sub-tree for that root and make that our ancestor instance.
-        let node = targetInst;
+    // If we are using the legacy FB support flag, we
+    // defer the event to the null with a one
+    // time event listener so we can defer the event.
+    if (
+      enableLegacyFBSupport &&
+      // We do not want to defer if the event system has already been
+      // set to LEGACY_FB_SUPPORT. LEGACY_FB_SUPPORT only gets set when
+      // we call willDeferLaterForLegacyFBSupport, thus not bailing out
+      // will result in endless cycles like an infinite loop.
+      (eventSystemFlags & LEGACY_FB_SUPPORT) === 0 &&
+      // We also don't want to defer during event replaying.
+      (eventSystemFlags & IS_REPLAYED) === 0 &&
+      // We don't want to apply the legacy FB support for the useEvent API.
+      (eventSystemFlags & USE_EVENT_SYSTEM) === 0 &&
+      willDeferLaterForLegacyFBSupport(topLevelType, targetContainer)
+    ) {
+      return;
+    }
+    if (targetInst !== null) {
+      // The below logic attempts to work out if we need to change
+      // the target fiber to a different ancestor. We had similar logic
+      // in the legacy event system, except the big difference between
+      // systems is that the modern event system now has an event listener
+      // attached to each React Root and React Portal Root. Together,
+      // the DOM nodes representing these roots are the "rootContainer".
+      // To figure out which ancestor instance we should use, we traverse
+      // up the fiber tree from the target instance and attempt to find
+      // root boundaries that match that of our current "rootContainer".
+      // If we find that "rootContainer", we find the parent fiber
+      // sub-tree for that root and make that our ancestor instance.
+      let node = targetInst;
 
-        while (true) {
-          if (node === null) {
+      while (true) {
+        if (node === null) {
+          return;
+        }
+        if (node.tag === HostRoot || node.tag === HostPortal) {
+          const container = node.stateNode.containerInfo;
+          if (isMatchingRootContainer(container, targetContainerNode)) {
+            break;
+          }
+          if (node.tag === HostPortal) {
+            // The target is a portal, but it's not the rootContainer we're looking for.
+            // Normally portals handle their own events all the way down to the root.
+            // So we should be able to stop now. However, we don't know if this portal
+            // was part of *our* root.
+            let grandNode = node.return;
+            while (grandNode !== null) {
+              if (grandNode.tag === HostRoot || grandNode.tag === HostPortal) {
+                const grandContainer = grandNode.stateNode.containerInfo;
+                if (
+                  isMatchingRootContainer(grandContainer, targetContainerNode)
+                ) {
+                  // This is the rootContainer we're looking for and we found it as
+                  // a parent of the Portal. That means we can ignore it because the
+                  // Portal will bubble through to us.
+                  return;
+                }
+              }
+              grandNode = grandNode.return;
+            }
+          }
+          const parentSubtreeInst = getClosestInstanceFromNode(container);
+          if (parentSubtreeInst === null) {
             return;
           }
-          if (node.tag === HostRoot || node.tag === HostPortal) {
-            const container = node.stateNode.containerInfo;
-            if (isMatchingRootContainer(container, targetContainerNode)) {
-              break;
-            }
-            if (node.tag === HostPortal) {
-              // The target is a portal, but it's not the rootContainer we're looking for.
-              // Normally portals handle their own events all the way down to the root.
-              // So we should be able to stop now. However, we don't know if this portal
-              // was part of *our* root.
-              let grandNode = node.return;
-              while (grandNode !== null) {
-                if (
-                  grandNode.tag === HostRoot ||
-                  grandNode.tag === HostPortal
-                ) {
-                  const grandContainer = grandNode.stateNode.containerInfo;
-                  if (
-                    isMatchingRootContainer(grandContainer, targetContainerNode)
-                  ) {
-                    // This is the rootContainer we're looking for and we found it as
-                    // a parent of the Portal. That means we can ignore it because the
-                    // Portal will bubble through to us.
-                    return;
-                  }
-                }
-                grandNode = grandNode.return;
-              }
-            }
-            const parentSubtreeInst = getClosestInstanceFromNode(container);
-            if (parentSubtreeInst === null) {
-              return;
-            }
-            node = ancestorInst = parentSubtreeInst;
-            continue;
-          }
-          node = node.return;
+          node = ancestorInst = parentSubtreeInst;
+          continue;
         }
+        node = node.return;
       }
     }
   }
diff --git a/packages/react-dom/src/events/ReactDOMEventListener.js b/packages/react-dom/src/events/ReactDOMEventListener.js
index 2d6e5c3296..af3d59da55 100644
--- a/packages/react-dom/src/events/ReactDOMEventListener.js
+++ b/packages/react-dom/src/events/ReactDOMEventListener.js
@@ -165,16 +165,6 @@ export function addTrappedEventListener(
     targetContainer,
   );
 
-  // When the targetContainer is null, it means that the container
-  // target is null, but really we need a real DOM node to attach to.
-  // In this case, we fallback to the "document" node, but leave the
-  // targetContainer (which is bound in the above function) to null.
-  // Really, this only happens for TestUtils.Simulate, so when we
-  // remove that support, we can remove this block of code.
-  if (targetContainer === null) {
-    targetContainer = document;
-  }
-
   targetContainer =
     enableLegacyFBSupport && isDeferredListenerForLegacyFBSupport
       ? (targetContainer: any).ownerDocument
@@ -299,7 +289,7 @@ function dispatchUserBlockingUpdate(
 export function dispatchEvent(
   topLevelType: DOMTopLevelEventType,
   eventSystemFlags: EventSystemFlags,
-  targetContainer: null | EventTarget,
+  targetContainer: EventTarget,
   nativeEvent: AnyNativeEvent,
 ): void {
   if (!_enabled) {
@@ -415,7 +405,7 @@ export function dispatchEvent(
 export function attemptToDispatchEvent(
   topLevelType: DOMTopLevelEventType,
   eventSystemFlags: EventSystemFlags,
-  targetContainer: EventTarget | null,
+  targetContainer: EventTarget,
   nativeEvent: AnyNativeEvent,
 ): null | Container | SuspenseInstance {
   // TODO: Warn if _enabled is false.
diff --git a/packages/react-dom/src/events/ReactDOMEventReplaying.js b/packages/react-dom/src/events/ReactDOMEventReplaying.js
index b45fe37d8b..8f57eb26a2 100644
--- a/packages/react-dom/src/events/ReactDOMEventReplaying.js
+++ b/packages/react-dom/src/events/ReactDOMEventReplaying.js
@@ -291,7 +291,7 @@ function createQueuedReplayableEvent(
   blockedOn: null | Container | SuspenseInstance,
   topLevelType: DOMTopLevelEventType,
   eventSystemFlags: EventSystemFlags,
-  targetContainer: EventTarget | null,
+  targetContainer: EventTarget,
   nativeEvent: AnyNativeEvent,
 ): QueuedReplayableEvent {
   return {
@@ -299,7 +299,7 @@ function createQueuedReplayableEvent(
     topLevelType,
     eventSystemFlags: eventSystemFlags | IS_REPLAYED,
     nativeEvent,
-    targetContainers: targetContainer !== null ? [targetContainer] : [],
+    targetContainers: [targetContainer],
   };
 }
 
@@ -307,7 +307,7 @@ export function queueDiscreteEvent(
   blockedOn: null | Container | SuspenseInstance,
   topLevelType: DOMTopLevelEventType,
   eventSystemFlags: EventSystemFlags,
-  targetContainer: EventTarget | null,
+  targetContainer: EventTarget,
   nativeEvent: AnyNativeEvent,
 ): void {
   const queuedEvent = createQueuedReplayableEvent(
@@ -382,7 +382,7 @@ function accumulateOrCreateContinuousQueuedReplayableEvent(
   blockedOn: null | Container | SuspenseInstance,
   topLevelType: DOMTopLevelEventType,
   eventSystemFlags: EventSystemFlags,
-  targetContainer: EventTarget | null,
+  targetContainer: EventTarget,
   nativeEvent: AnyNativeEvent,
 ): QueuedReplayableEvent {
   if (
@@ -424,7 +424,7 @@ export function queueIfContinuousEvent(
   blockedOn: null | Container | SuspenseInstance,
   topLevelType: DOMTopLevelEventType,
   eventSystemFlags: EventSystemFlags,
-  targetContainer: EventTarget | null,
+  targetContainer: EventTarget,
   nativeEvent: AnyNativeEvent,
 ): boolean {
   // These set relatedTarget to null because the replayed event will be treated as if we
diff --git a/packages/react-dom/src/test-utils/ReactTestUtils.js b/packages/react-dom/src/test-utils/ReactTestUtils.js
index b5f0f9e433..2348a047ba 100644
--- a/packages/react-dom/src/test-utils/ReactTestUtils.js
+++ b/packages/react-dom/src/test-utils/ReactTestUtils.js
@@ -22,6 +22,7 @@ import * as DOMTopLevelEventTypes from '../events/DOMTopLevelEventTypes';
 import act from './ReactTestUtilsAct';
 import forEachAccumulated from 'legacy-events/forEachAccumulated';
 import accumulateInto from 'legacy-events/accumulateInto';
+import {enableModernEventSystem} from 'shared/ReactFeatureFlags';
 
 const {findDOMNode} = ReactDOM;
 // Keep in sync with ReactDOMUnstableNativeDependencies.js
@@ -53,34 +54,6 @@ let didWarnSimulateNativeDeprecated = false;
  * @class ReactTestUtils
  */
 
-/**
- * Simulates a top level event being dispatched from a raw event that occurred
- * on an `Element` node.
- * @param {number} topLevelType A number from `TopLevelEventTypes`
- * @param {!Element} node The dom to simulate an event occurring on.
- * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
- */
-function simulateNativeEventOnNode(topLevelType, node, fakeNativeEvent) {
-  fakeNativeEvent.target = node;
-  const PLUGIN_EVENT_SYSTEM = 1;
-  dispatchEvent(topLevelType, PLUGIN_EVENT_SYSTEM, null, fakeNativeEvent);
-}
-
-/**
- * Simulates a top level event being dispatched from a raw event that occurred
- * on the `ReactDOMComponent` `comp`.
- * @param {Object} topLevelType A type from `BrowserEventConstants.topLevelTypes`.
- * @param {!ReactDOMComponent} comp
- * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
- */
-function simulateNativeEventOnDOMComponent(
-  topLevelType,
-  comp,
-  fakeNativeEvent,
-) {
-  simulateNativeEventOnNode(topLevelType, findDOMNode(comp), fakeNativeEvent);
-}
-
 function findAllInRenderedFiberTreeInternal(fiber, test) {
   if (!fiber) {
     return [];
@@ -531,7 +504,7 @@ function accumulateTwoPhaseDispatches(events) {
 // End of inline
 
 const Simulate = {};
-const SimulateNative = {};
+let SimulateNative;
 
 /**
  * Exports:
@@ -605,134 +578,170 @@ function buildSimulators() {
 
 buildSimulators();
 
-/**
- * Exports:
- *
- * - `SimulateNative.click(Element/ReactDOMComponent)`
- * - `SimulateNative.mouseMove(Element/ReactDOMComponent)`
- * - `SimulateNative.mouseIn/ReactDOMComponent)`
- * - `SimulateNative.mouseOut(Element/ReactDOMComponent)`
- * - ... (All keys from `BrowserEventConstants.topLevelTypes`)
- *
- * Note: Top level event types are a subset of the entire set of handler types
- * (which include a broader set of "synthetic" events). For example, onDragDone
- * is a synthetic event. Except when testing an event plugin or React's event
- * handling code specifically, you probably want to use Simulate
- * to dispatch synthetic events.
- */
+if (!enableModernEventSystem) {
+  SimulateNative = {};
 
-function makeNativeSimulator(eventType, topLevelType) {
-  return function(domComponentOrNode, nativeEventData) {
-    if (__DEV__) {
-      if (!didWarnSimulateNativeDeprecated) {
-        didWarnSimulateNativeDeprecated = true;
-        console.warn(
-          'ReactTestUtils.SimulateNative is an undocumented API that does not match ' +
-            'how the browser dispatches events, and will be removed in a future major ' +
-            'version of React. If you rely on it for testing, consider attaching the root ' +
-            'DOM container to the document during the test, and then dispatching native browser ' +
-            'events by calling `node.dispatchEvent()` on the DOM nodes. Make sure to set ' +
-            'the `bubbles` flag to `true` when creating the native browser event.',
+  /**
+   * Simulates a top level event being dispatched from a raw event that occurred
+   * on an `Element` node.
+   * @param {number} topLevelType A number from `TopLevelEventTypes`
+   * @param {!Element} node The dom to simulate an event occurring on.
+   * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
+   */
+  const simulateNativeEventOnNode = function(
+    topLevelType,
+    node,
+    fakeNativeEvent,
+  ) {
+    fakeNativeEvent.target = node;
+    const PLUGIN_EVENT_SYSTEM = 1;
+    dispatchEvent(topLevelType, PLUGIN_EVENT_SYSTEM, null, fakeNativeEvent);
+  };
+
+  /**
+   * Simulates a top level event being dispatched from a raw event that occurred
+   * on the `ReactDOMComponent` `comp`.
+   * @param {Object} topLevelType A type from `BrowserEventConstants.topLevelTypes`.
+   * @param {!ReactDOMComponent} comp
+   * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
+   */
+  const simulateNativeEventOnDOMComponent = function(
+    topLevelType,
+    comp,
+    fakeNativeEvent,
+  ) {
+    simulateNativeEventOnNode(topLevelType, findDOMNode(comp), fakeNativeEvent);
+  };
+
+  /**
+   * Exports:
+   *
+   * - `SimulateNative.click(Element/ReactDOMComponent)`
+   * - `SimulateNative.mouseMove(Element/ReactDOMComponent)`
+   * - `SimulateNative.mouseIn/ReactDOMComponent)`
+   * - `SimulateNative.mouseOut(Element/ReactDOMComponent)`
+   * - ... (All keys from `BrowserEventConstants.topLevelTypes`)
+   *
+   * Note: Top level event types are a subset of the entire set of handler types
+   * (which include a broader set of "synthetic" events). For example, onDragDone
+   * is a synthetic event. Except when testing an event plugin or React's event
+   * handling code specifically, you probably want to use Simulate
+   * to dispatch synthetic events.
+   */
+
+  const makeNativeSimulator = function(eventType, topLevelType) {
+    return function(domComponentOrNode, nativeEventData) {
+      if (__DEV__) {
+        if (!didWarnSimulateNativeDeprecated) {
+          didWarnSimulateNativeDeprecated = true;
+          console.warn(
+            'ReactTestUtils.SimulateNative is an undocumented API that does not match ' +
+              'how the browser dispatches events, and will be removed in a future major ' +
+              'version of React. If you rely on it for testing, consider attaching the root ' +
+              'DOM container to the document during the test, and then dispatching native browser ' +
+              'events by calling `node.dispatchEvent()` on the DOM nodes. Make sure to set ' +
+              'the `bubbles` flag to `true` when creating the native browser event.',
+          );
+        }
+      }
+
+      const fakeNativeEvent = new Event(eventType);
+      Object.assign(fakeNativeEvent, nativeEventData);
+      if (isDOMComponent(domComponentOrNode)) {
+        simulateNativeEventOnDOMComponent(
+          topLevelType,
+          domComponentOrNode,
+          fakeNativeEvent,
+        );
+      } else if (domComponentOrNode.tagName) {
+        // Will allow on actual dom nodes.
+        simulateNativeEventOnNode(
+          topLevelType,
+          domComponentOrNode,
+          fakeNativeEvent,
         );
       }
-    }
-
-    const fakeNativeEvent = new Event(eventType);
-    Object.assign(fakeNativeEvent, nativeEventData);
-    if (isDOMComponent(domComponentOrNode)) {
-      simulateNativeEventOnDOMComponent(
-        topLevelType,
-        domComponentOrNode,
-        fakeNativeEvent,
-      );
-    } else if (domComponentOrNode.tagName) {
-      // Will allow on actual dom nodes.
-      simulateNativeEventOnNode(
-        topLevelType,
-        domComponentOrNode,
-        fakeNativeEvent,
-      );
-    }
+    };
   };
-}
 
-[
-  [DOMTopLevelEventTypes.TOP_ABORT, 'abort'],
-  [DOMTopLevelEventTypes.TOP_ANIMATION_END, 'animationEnd'],
-  [DOMTopLevelEventTypes.TOP_ANIMATION_ITERATION, 'animationIteration'],
-  [DOMTopLevelEventTypes.TOP_ANIMATION_START, 'animationStart'],
-  [DOMTopLevelEventTypes.TOP_BLUR, 'blur'],
-  [DOMTopLevelEventTypes.TOP_CAN_PLAY_THROUGH, 'canPlayThrough'],
-  [DOMTopLevelEventTypes.TOP_CAN_PLAY, 'canPlay'],
-  [DOMTopLevelEventTypes.TOP_CANCEL, 'cancel'],
-  [DOMTopLevelEventTypes.TOP_CHANGE, 'change'],
-  [DOMTopLevelEventTypes.TOP_CLICK, 'click'],
-  [DOMTopLevelEventTypes.TOP_CLOSE, 'close'],
-  [DOMTopLevelEventTypes.TOP_COMPOSITION_END, 'compositionEnd'],
-  [DOMTopLevelEventTypes.TOP_COMPOSITION_START, 'compositionStart'],
-  [DOMTopLevelEventTypes.TOP_COMPOSITION_UPDATE, 'compositionUpdate'],
-  [DOMTopLevelEventTypes.TOP_CONTEXT_MENU, 'contextMenu'],
-  [DOMTopLevelEventTypes.TOP_COPY, 'copy'],
-  [DOMTopLevelEventTypes.TOP_CUT, 'cut'],
-  [DOMTopLevelEventTypes.TOP_DOUBLE_CLICK, 'doubleClick'],
-  [DOMTopLevelEventTypes.TOP_DRAG_END, 'dragEnd'],
-  [DOMTopLevelEventTypes.TOP_DRAG_ENTER, 'dragEnter'],
-  [DOMTopLevelEventTypes.TOP_DRAG_EXIT, 'dragExit'],
-  [DOMTopLevelEventTypes.TOP_DRAG_LEAVE, 'dragLeave'],
-  [DOMTopLevelEventTypes.TOP_DRAG_OVER, 'dragOver'],
-  [DOMTopLevelEventTypes.TOP_DRAG_START, 'dragStart'],
-  [DOMTopLevelEventTypes.TOP_DRAG, 'drag'],
-  [DOMTopLevelEventTypes.TOP_DROP, 'drop'],
-  [DOMTopLevelEventTypes.TOP_DURATION_CHANGE, 'durationChange'],
-  [DOMTopLevelEventTypes.TOP_EMPTIED, 'emptied'],
-  [DOMTopLevelEventTypes.TOP_ENCRYPTED, 'encrypted'],
-  [DOMTopLevelEventTypes.TOP_ENDED, 'ended'],
-  [DOMTopLevelEventTypes.TOP_ERROR, 'error'],
-  [DOMTopLevelEventTypes.TOP_FOCUS, 'focus'],
-  [DOMTopLevelEventTypes.TOP_INPUT, 'input'],
-  [DOMTopLevelEventTypes.TOP_KEY_DOWN, 'keyDown'],
-  [DOMTopLevelEventTypes.TOP_KEY_PRESS, 'keyPress'],
-  [DOMTopLevelEventTypes.TOP_KEY_UP, 'keyUp'],
-  [DOMTopLevelEventTypes.TOP_LOAD_START, 'loadStart'],
-  [DOMTopLevelEventTypes.TOP_LOAD_START, 'loadStart'],
-  [DOMTopLevelEventTypes.TOP_LOAD, 'load'],
-  [DOMTopLevelEventTypes.TOP_LOADED_DATA, 'loadedData'],
-  [DOMTopLevelEventTypes.TOP_LOADED_METADATA, 'loadedMetadata'],
-  [DOMTopLevelEventTypes.TOP_MOUSE_DOWN, 'mouseDown'],
-  [DOMTopLevelEventTypes.TOP_MOUSE_MOVE, 'mouseMove'],
-  [DOMTopLevelEventTypes.TOP_MOUSE_OUT, 'mouseOut'],
-  [DOMTopLevelEventTypes.TOP_MOUSE_OVER, 'mouseOver'],
-  [DOMTopLevelEventTypes.TOP_MOUSE_UP, 'mouseUp'],
-  [DOMTopLevelEventTypes.TOP_PASTE, 'paste'],
-  [DOMTopLevelEventTypes.TOP_PAUSE, 'pause'],
-  [DOMTopLevelEventTypes.TOP_PLAY, 'play'],
-  [DOMTopLevelEventTypes.TOP_PLAYING, 'playing'],
-  [DOMTopLevelEventTypes.TOP_PROGRESS, 'progress'],
-  [DOMTopLevelEventTypes.TOP_RATE_CHANGE, 'rateChange'],
-  [DOMTopLevelEventTypes.TOP_SCROLL, 'scroll'],
-  [DOMTopLevelEventTypes.TOP_SEEKED, 'seeked'],
-  [DOMTopLevelEventTypes.TOP_SEEKING, 'seeking'],
-  [DOMTopLevelEventTypes.TOP_SELECTION_CHANGE, 'selectionChange'],
-  [DOMTopLevelEventTypes.TOP_STALLED, 'stalled'],
-  [DOMTopLevelEventTypes.TOP_SUSPEND, 'suspend'],
-  [DOMTopLevelEventTypes.TOP_TEXT_INPUT, 'textInput'],
-  [DOMTopLevelEventTypes.TOP_TIME_UPDATE, 'timeUpdate'],
-  [DOMTopLevelEventTypes.TOP_TOGGLE, 'toggle'],
-  [DOMTopLevelEventTypes.TOP_TOUCH_CANCEL, 'touchCancel'],
-  [DOMTopLevelEventTypes.TOP_TOUCH_END, 'touchEnd'],
-  [DOMTopLevelEventTypes.TOP_TOUCH_MOVE, 'touchMove'],
-  [DOMTopLevelEventTypes.TOP_TOUCH_START, 'touchStart'],
-  [DOMTopLevelEventTypes.TOP_TRANSITION_END, 'transitionEnd'],
-  [DOMTopLevelEventTypes.TOP_VOLUME_CHANGE, 'volumeChange'],
-  [DOMTopLevelEventTypes.TOP_WAITING, 'waiting'],
-  [DOMTopLevelEventTypes.TOP_WHEEL, 'wheel'],
-].forEach(([topLevelType, eventType]) => {
-  /**
-   * @param {!Element|ReactDOMComponent} domComponentOrNode
-   * @param {?Event} nativeEventData Fake native event to use in SyntheticEvent.
-   */
-  SimulateNative[eventType] = makeNativeSimulator(eventType, topLevelType);
-});
+  [
+    [DOMTopLevelEventTypes.TOP_ABORT, 'abort'],
+    [DOMTopLevelEventTypes.TOP_ANIMATION_END, 'animationEnd'],
+    [DOMTopLevelEventTypes.TOP_ANIMATION_ITERATION, 'animationIteration'],
+    [DOMTopLevelEventTypes.TOP_ANIMATION_START, 'animationStart'],
+    [DOMTopLevelEventTypes.TOP_BLUR, 'blur'],
+    [DOMTopLevelEventTypes.TOP_CAN_PLAY_THROUGH, 'canPlayThrough'],
+    [DOMTopLevelEventTypes.TOP_CAN_PLAY, 'canPlay'],
+    [DOMTopLevelEventTypes.TOP_CANCEL, 'cancel'],
+    [DOMTopLevelEventTypes.TOP_CHANGE, 'change'],
+    [DOMTopLevelEventTypes.TOP_CLICK, 'click'],
+    [DOMTopLevelEventTypes.TOP_CLOSE, 'close'],
+    [DOMTopLevelEventTypes.TOP_COMPOSITION_END, 'compositionEnd'],
+    [DOMTopLevelEventTypes.TOP_COMPOSITION_START, 'compositionStart'],
+    [DOMTopLevelEventTypes.TOP_COMPOSITION_UPDATE, 'compositionUpdate'],
+    [DOMTopLevelEventTypes.TOP_CONTEXT_MENU, 'contextMenu'],
+    [DOMTopLevelEventTypes.TOP_COPY, 'copy'],
+    [DOMTopLevelEventTypes.TOP_CUT, 'cut'],
+    [DOMTopLevelEventTypes.TOP_DOUBLE_CLICK, 'doubleClick'],
+    [DOMTopLevelEventTypes.TOP_DRAG_END, 'dragEnd'],
+    [DOMTopLevelEventTypes.TOP_DRAG_ENTER, 'dragEnter'],
+    [DOMTopLevelEventTypes.TOP_DRAG_EXIT, 'dragExit'],
+    [DOMTopLevelEventTypes.TOP_DRAG_LEAVE, 'dragLeave'],
+    [DOMTopLevelEventTypes.TOP_DRAG_OVER, 'dragOver'],
+    [DOMTopLevelEventTypes.TOP_DRAG_START, 'dragStart'],
+    [DOMTopLevelEventTypes.TOP_DRAG, 'drag'],
+    [DOMTopLevelEventTypes.TOP_DROP, 'drop'],
+    [DOMTopLevelEventTypes.TOP_DURATION_CHANGE, 'durationChange'],
+    [DOMTopLevelEventTypes.TOP_EMPTIED, 'emptied'],
+    [DOMTopLevelEventTypes.TOP_ENCRYPTED, 'encrypted'],
+    [DOMTopLevelEventTypes.TOP_ENDED, 'ended'],
+    [DOMTopLevelEventTypes.TOP_ERROR, 'error'],
+    [DOMTopLevelEventTypes.TOP_FOCUS, 'focus'],
+    [DOMTopLevelEventTypes.TOP_INPUT, 'input'],
+    [DOMTopLevelEventTypes.TOP_KEY_DOWN, 'keyDown'],
+    [DOMTopLevelEventTypes.TOP_KEY_PRESS, 'keyPress'],
+    [DOMTopLevelEventTypes.TOP_KEY_UP, 'keyUp'],
+    [DOMTopLevelEventTypes.TOP_LOAD_START, 'loadStart'],
+    [DOMTopLevelEventTypes.TOP_LOAD_START, 'loadStart'],
+    [DOMTopLevelEventTypes.TOP_LOAD, 'load'],
+    [DOMTopLevelEventTypes.TOP_LOADED_DATA, 'loadedData'],
+    [DOMTopLevelEventTypes.TOP_LOADED_METADATA, 'loadedMetadata'],
+    [DOMTopLevelEventTypes.TOP_MOUSE_DOWN, 'mouseDown'],
+    [DOMTopLevelEventTypes.TOP_MOUSE_MOVE, 'mouseMove'],
+    [DOMTopLevelEventTypes.TOP_MOUSE_OUT, 'mouseOut'],
+    [DOMTopLevelEventTypes.TOP_MOUSE_OVER, 'mouseOver'],
+    [DOMTopLevelEventTypes.TOP_MOUSE_UP, 'mouseUp'],
+    [DOMTopLevelEventTypes.TOP_PASTE, 'paste'],
+    [DOMTopLevelEventTypes.TOP_PAUSE, 'pause'],
+    [DOMTopLevelEventTypes.TOP_PLAY, 'play'],
+    [DOMTopLevelEventTypes.TOP_PLAYING, 'playing'],
+    [DOMTopLevelEventTypes.TOP_PROGRESS, 'progress'],
+    [DOMTopLevelEventTypes.TOP_RATE_CHANGE, 'rateChange'],
+    [DOMTopLevelEventTypes.TOP_SCROLL, 'scroll'],
+    [DOMTopLevelEventTypes.TOP_SEEKED, 'seeked'],
+    [DOMTopLevelEventTypes.TOP_SEEKING, 'seeking'],
+    [DOMTopLevelEventTypes.TOP_SELECTION_CHANGE, 'selectionChange'],
+    [DOMTopLevelEventTypes.TOP_STALLED, 'stalled'],
+    [DOMTopLevelEventTypes.TOP_SUSPEND, 'suspend'],
+    [DOMTopLevelEventTypes.TOP_TEXT_INPUT, 'textInput'],
+    [DOMTopLevelEventTypes.TOP_TIME_UPDATE, 'timeUpdate'],
+    [DOMTopLevelEventTypes.TOP_TOGGLE, 'toggle'],
+    [DOMTopLevelEventTypes.TOP_TOUCH_CANCEL, 'touchCancel'],
+    [DOMTopLevelEventTypes.TOP_TOUCH_END, 'touchEnd'],
+    [DOMTopLevelEventTypes.TOP_TOUCH_MOVE, 'touchMove'],
+    [DOMTopLevelEventTypes.TOP_TOUCH_START, 'touchStart'],
+    [DOMTopLevelEventTypes.TOP_TRANSITION_END, 'transitionEnd'],
+    [DOMTopLevelEventTypes.TOP_VOLUME_CHANGE, 'volumeChange'],
+    [DOMTopLevelEventTypes.TOP_WAITING, 'waiting'],
+    [DOMTopLevelEventTypes.TOP_WHEEL, 'wheel'],
+  ].forEach(([topLevelType, eventType]) => {
+    /**
+     * @param {!Element|ReactDOMComponent} domComponentOrNode
+     * @param {?Event} nativeEventData Fake native event to use in SyntheticEvent.
+     */
+    SimulateNative[eventType] = makeNativeSimulator(eventType, topLevelType);
+  });
+}
 
 export {
   renderIntoDocument,