From 172e89b4bf0ec5ee5738af0156d90b0deef4d494 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Markb=C3=A5ge?= <sema@fb.com>
Date: Wed, 7 Apr 2021 10:57:43 -0400
Subject: [PATCH] Reland Remove redundant initial of isArray (#21188)

* Remove redundant initial of isArray (#21163)

* Reapply prettier

* Type the isArray function with refinement support

This ensures that an argument gets refined just like it does if isArray is
used directly.

I'm not sure how to express with just a direct reference so I added a
function wrapper and confirmed that this does get inlined properly by
closure compiler.

* A few more

* Rename unit test to internal

This is not testing a bundle.

Co-authored-by: Behnam Mohammadi <itten@live.com>
---
 .../src/ExhaustiveDeps.js                     | 13 ++++++-------
 packages/jest-react/src/JestReact.js          |  3 ++-
 .../src/backend/renderer.js                   |  3 ++-
 .../src/backend/utils.js                      | 11 ++++++-----
 .../react-dom/src/client/ReactDOMSelect.js    |  7 ++++---
 .../react-dom/src/client/ReactDOMTextarea.js  |  4 ++--
 .../src/server/ReactDOMServerFormatConfig.js  |  3 +--
 .../src/server/ReactPartialRenderer.js        | 11 ++++++-----
 .../src/test-utils/ReactTestUtils.js          |  7 ++++---
 .../src/ReactNativeAttributePayload.js        | 13 +++++++------
 ...ctNativeAttributePayload-test.internal.js} |  0
 .../src/legacy-events/EventPluginUtils.js     | 11 ++++++-----
 .../src/legacy-events/accumulate.js           |  5 +++--
 .../src/legacy-events/accumulateInto.js       |  7 ++++---
 .../src/createReactNoop.js                    |  9 +++++----
 .../src/ReactChildFiber.new.js                |  3 +--
 .../src/ReactChildFiber.old.js                |  3 +--
 .../src/ReactFiberBeginWork.new.js            | 11 ++++++-----
 .../src/ReactFiberBeginWork.old.js            | 11 ++++++-----
 .../src/ReactFiberClassComponent.new.js       |  2 +-
 .../src/ReactFiberClassComponent.old.js       |  2 +-
 .../src/ReactFiberHooks.new.js                |  3 ++-
 .../src/ReactFiberHooks.old.js                |  3 ++-
 .../src/ReactFiberReconciler.new.js           | 11 ++++++-----
 .../src/ReactFiberReconciler.old.js           | 11 ++++++-----
 .../ReactFlightDOMRelayClientHostConfig.js    |  4 +++-
 .../ReactFlightDOMRelayServerHostConfig.js    |  3 ++-
 .../src/ReactFlightWebpackPlugin.js           |  4 +++-
 .../ReactFlightNativeRelayClientHostConfig.js |  4 +++-
 .../ReactFlightNativeRelayServerHostConfig.js |  4 ++--
 packages/react-server/src/ReactFizzServer.js  |  3 ++-
 .../react-server/src/ReactFlightServer.js     |  3 +--
 .../src/ReactTestHostConfig.js                |  3 ++-
 .../src/ReactTestRenderer.js                  |  3 ++-
 packages/react/src/ReactChildren.js           |  5 +++--
 packages/react/src/ReactElementValidator.js   |  9 +++++----
 .../react/src/jsx/ReactJSXElementValidator.js |  7 ++++---
 packages/shared/isArray.js                    | 19 +++++++++++++++++++
 38 files changed, 141 insertions(+), 97 deletions(-)
 rename packages/react-native-renderer/src/__tests__/{ReactNativeAttributePayload-test.js => ReactNativeAttributePayload-test.internal.js} (100%)
 create mode 100644 packages/shared/isArray.js

diff --git a/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js b/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js
index 2c76ca5991f76..f4c36fcf2202d 100644
--- a/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js
+++ b/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js
@@ -145,6 +145,8 @@ export default {
         componentScope = currentScope;
       }
 
+      const isArray = Array.isArray;
+
       // Next we'll define a few helpers that helps us
       // tell if some values don't have to be declared as deps.
 
@@ -157,7 +159,7 @@ export default {
       //       ^^^ true for this reference
       // False for everything else.
       function isStableKnownHookValue(resolved) {
-        if (!Array.isArray(resolved.defs)) {
+        if (!isArray(resolved.defs)) {
           return false;
         }
         const def = resolved.defs[0];
@@ -226,7 +228,7 @@ export default {
           if (
             id.type === 'ArrayPattern' &&
             id.elements.length === 2 &&
-            Array.isArray(resolved.identifiers)
+            isArray(resolved.identifiers)
           ) {
             // Is second tuple value the same reference we're checking?
             if (id.elements[1] === resolved.identifiers[0]) {
@@ -253,10 +255,7 @@ export default {
             }
           }
         } else if (name === 'useTransition') {
-          if (
-            id.type === 'ArrayPattern' &&
-            Array.isArray(resolved.identifiers)
-          ) {
+          if (id.type === 'ArrayPattern' && isArray(resolved.identifiers)) {
             // Is first tuple value the same reference we're checking?
             if (id.elements[0] === resolved.identifiers[0]) {
               // Setter is stable.
@@ -270,7 +269,7 @@ export default {
 
       // Some are just functions that don't reference anything dynamic.
       function isFunctionWithoutCapturedValues(resolved) {
-        if (!Array.isArray(resolved.defs)) {
+        if (!isArray(resolved.defs)) {
           return false;
         }
         const def = resolved.defs[0];
diff --git a/packages/jest-react/src/JestReact.js b/packages/jest-react/src/JestReact.js
index 57790797b966d..1f26cbee3a328 100644
--- a/packages/jest-react/src/JestReact.js
+++ b/packages/jest-react/src/JestReact.js
@@ -8,6 +8,7 @@
 import {REACT_ELEMENT_TYPE, REACT_FRAGMENT_TYPE} from 'shared/ReactSymbols';
 
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 
 function captureAssertion(fn) {
   // Trick to use a Jest matcher inside another Jest matcher. `fn` contains an
@@ -42,7 +43,7 @@ export function unstable_toMatchRenderedOutput(root, expectedJSX) {
   let actualJSX;
   if (actualJSON === null || typeof actualJSON === 'string') {
     actualJSX = actualJSON;
-  } else if (Array.isArray(actualJSON)) {
+  } else if (isArray(actualJSON)) {
     if (actualJSON.length === 0) {
       actualJSX = null;
     } else if (actualJSON.length === 1) {
diff --git a/packages/react-devtools-shared/src/backend/renderer.js b/packages/react-devtools-shared/src/backend/renderer.js
index 050a4e709ab32..c61edb45daa65 100644
--- a/packages/react-devtools-shared/src/backend/renderer.js
+++ b/packages/react-devtools-shared/src/backend/renderer.js
@@ -105,6 +105,7 @@ import type {
   ElementType,
 } from 'react-devtools-shared/src/types';
 import is from 'shared/objectIs';
+import isArray from 'shared/isArray';
 
 type getDisplayNameForFiberType = (fiber: Fiber) => string | null;
 type getTypeSymbolType = (type: any) => Symbol | number;
@@ -1137,7 +1138,7 @@ export function attach(
       memoizedState.hasOwnProperty('create') &&
       memoizedState.hasOwnProperty('destroy') &&
       memoizedState.hasOwnProperty('deps') &&
-      (memoizedState.deps === null || Array.isArray(memoizedState.deps)) &&
+      (memoizedState.deps === null || isArray(memoizedState.deps)) &&
       memoizedState.hasOwnProperty('next')
     );
   }
diff --git a/packages/react-devtools-shared/src/backend/utils.js b/packages/react-devtools-shared/src/backend/utils.js
index 7a4ff6295ab99..593459d78f646 100644
--- a/packages/react-devtools-shared/src/backend/utils.js
+++ b/packages/react-devtools-shared/src/backend/utils.js
@@ -9,6 +9,7 @@
 
 import {copy} from 'clipboard-js';
 import {dehydrate} from '../hydration';
+import isArray from 'shared/isArray';
 
 import type {DehydratedData} from 'react-devtools-shared/src/devtools/views/Components/types';
 
@@ -61,9 +62,9 @@ export function copyWithDelete(
   index: number = 0,
 ): Object | Array<any> {
   const key = path[index];
-  const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+  const updated = isArray(obj) ? obj.slice() : {...obj};
   if (index + 1 === path.length) {
-    if (Array.isArray(updated)) {
+    if (isArray(updated)) {
       updated.splice(((key: any): number), 1);
     } else {
       delete updated[key];
@@ -84,12 +85,12 @@ export function copyWithRename(
   index: number = 0,
 ): Object | Array<any> {
   const oldKey = oldPath[index];
-  const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+  const updated = isArray(obj) ? obj.slice() : {...obj};
   if (index + 1 === oldPath.length) {
     const newKey = newPath[index];
     // $FlowFixMe number or string is fine here
     updated[newKey] = updated[oldKey];
-    if (Array.isArray(updated)) {
+    if (isArray(updated)) {
       updated.splice(((oldKey: any): number), 1);
     } else {
       delete updated[oldKey];
@@ -111,7 +112,7 @@ export function copyWithSet(
     return value;
   }
   const key = path[index];
-  const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+  const updated = isArray(obj) ? obj.slice() : {...obj};
   // $FlowFixMe number or string is fine here
   updated[key] = copyWithSet(obj[key], path, value, index + 1);
   return updated;
diff --git a/packages/react-dom/src/client/ReactDOMSelect.js b/packages/react-dom/src/client/ReactDOMSelect.js
index 1efca61905b4a..df336d4b92254 100644
--- a/packages/react-dom/src/client/ReactDOMSelect.js
+++ b/packages/react-dom/src/client/ReactDOMSelect.js
@@ -12,6 +12,7 @@ import {getCurrentFiberOwnerNameInDevOrNull} from 'react-reconciler/src/ReactCur
 
 import {checkControlledValueProps} from '../shared/ReactControlledValuePropTypes';
 import {getToStringValue, toString} from './ToStringValue';
+import isArray from 'shared/isArray';
 
 let didWarnValueDefaultValue;
 
@@ -45,15 +46,15 @@ function checkSelectPropTypes(props) {
       if (props[propName] == null) {
         continue;
       }
-      const isArray = Array.isArray(props[propName]);
-      if (props.multiple && !isArray) {
+      const propNameIsArray = isArray(props[propName]);
+      if (props.multiple && !propNameIsArray) {
         console.error(
           'The `%s` prop supplied to <select> must be an array if ' +
             '`multiple` is true.%s',
           propName,
           getDeclarationErrorAddendum(),
         );
-      } else if (!props.multiple && isArray) {
+      } else if (!props.multiple && propNameIsArray) {
         console.error(
           'The `%s` prop supplied to <select> must be a scalar ' +
             'value if `multiple` is false.%s',
diff --git a/packages/react-dom/src/client/ReactDOMTextarea.js b/packages/react-dom/src/client/ReactDOMTextarea.js
index 24fb591fcd8af..6e8aed5cc43cd 100644
--- a/packages/react-dom/src/client/ReactDOMTextarea.js
+++ b/packages/react-dom/src/client/ReactDOMTextarea.js
@@ -8,12 +8,12 @@
  */
 
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 
 import {checkControlledValueProps} from '../shared/ReactControlledValuePropTypes';
 import {getCurrentFiberOwnerNameInDevOrNull} from 'react-reconciler/src/ReactCurrentFiber';
 import {getToStringValue, toString} from './ToStringValue';
 import type {ToStringValue} from './ToStringValue';
-
 import {disableTextareaChildren} from 'shared/ReactFeatureFlags';
 
 let didWarnValDefaultVal = false;
@@ -100,7 +100,7 @@ export function initWrapperState(element: Element, props: Object) {
           defaultValue == null,
           'If you supply `defaultValue` on a <textarea>, do not pass children.',
         );
-        if (Array.isArray(children)) {
+        if (isArray(children)) {
           invariant(
             children.length <= 1,
             '<textarea> can only have at most one child.',
diff --git a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
index 2988e9a588334..45cd0fecb5e96 100644
--- a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
+++ b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
@@ -46,8 +46,7 @@ import hyphenateStyleName from '../shared/hyphenateStyleName';
 import invariant from 'shared/invariant';
 import hasOwnProperty from 'shared/hasOwnProperty';
 import sanitizeURL from '../shared/sanitizeURL';
-
-const isArray = Array.isArray;
+import isArray from 'shared/isArray';
 
 // Per response, global state that is not contextual to the rendering subtree.
 export type ResponseState = {
diff --git a/packages/react-dom/src/server/ReactPartialRenderer.js b/packages/react-dom/src/server/ReactPartialRenderer.js
index 4d2aeb5b38f81..90fbfd6ad4391 100644
--- a/packages/react-dom/src/server/ReactPartialRenderer.js
+++ b/packages/react-dom/src/server/ReactPartialRenderer.js
@@ -14,6 +14,7 @@ import type {ReactProvider, ReactContext} from 'shared/ReactTypes';
 
 import * as React from 'react';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 import {describeUnknownElementTypeFrameInDEV} from 'shared/ReactComponentStackFrame';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
@@ -1438,7 +1439,7 @@ class ReactDOMServerRenderer {
             defaultValue == null,
             'If you supply `defaultValue` on a <textarea>, do not pass children.',
           );
-          if (Array.isArray(textareaChildren)) {
+          if (isArray(textareaChildren)) {
             invariant(
               textareaChildren.length <= 1,
               '<textarea> can only have at most one child.',
@@ -1467,14 +1468,14 @@ class ReactDOMServerRenderer {
           if (props[propName] == null) {
             continue;
           }
-          const isArray = Array.isArray(props[propName]);
-          if (props.multiple && !isArray) {
+          const propNameIsArray = isArray(props[propName]);
+          if (props.multiple && !propNameIsArray) {
             console.error(
               'The `%s` prop supplied to <select> must be an array if ' +
                 '`multiple` is true.',
               propName,
             );
-          } else if (!props.multiple && isArray) {
+          } else if (!props.multiple && propNameIsArray) {
             console.error(
               'The `%s` prop supplied to <select> must be a scalar ' +
                 'value if `multiple` is false.',
@@ -1515,7 +1516,7 @@ class ReactDOMServerRenderer {
           value = optionChildren;
         }
         selected = false;
-        if (Array.isArray(selectValue)) {
+        if (isArray(selectValue)) {
           // multiple
           for (let j = 0; j < selectValue.length; j++) {
             if ('' + selectValue[j] === value) {
diff --git a/packages/react-dom/src/test-utils/ReactTestUtils.js b/packages/react-dom/src/test-utils/ReactTestUtils.js
index dc59d2a64420f..492ab02d11929 100644
--- a/packages/react-dom/src/test-utils/ReactTestUtils.js
+++ b/packages/react-dom/src/test-utils/ReactTestUtils.js
@@ -24,6 +24,7 @@ import {
   rethrowCaughtError,
   invokeGuardedCallbackAndCatchFirstError,
 } from 'shared/ReactErrorUtils';
+import isArray from 'shared/isArray';
 
 // Keep in sync with ReactDOM.js, and ReactTestUtilsAct.js:
 const EventInternals =
@@ -97,7 +98,7 @@ function validateClassInstance(inst, methodName) {
   }
   let received;
   const stringified = '' + inst;
-  if (Array.isArray(inst)) {
+  if (isArray(inst)) {
     received = 'an array';
   } else if (inst && inst.nodeType === ELEMENT_NODE && inst.tagName) {
     received = 'a DOM node';
@@ -197,7 +198,7 @@ function scryRenderedDOMComponentsWithClass(root, classNames) {
       }
       const classList = className.split(/\s+/);
 
-      if (!Array.isArray(classNames)) {
+      if (!isArray(classNames)) {
         invariant(
           classNames !== undefined,
           'TestUtils.scryRenderedDOMComponentsWithClass expects a ' +
@@ -365,7 +366,7 @@ function executeDispatch(event, listener, inst) {
 function executeDispatchesInOrder(event) {
   const dispatchListeners = event._dispatchListeners;
   const dispatchInstances = event._dispatchInstances;
-  if (Array.isArray(dispatchListeners)) {
+  if (isArray(dispatchListeners)) {
     for (let i = 0; i < dispatchListeners.length; i++) {
       if (event.isPropagationStopped()) {
         break;
diff --git a/packages/react-native-renderer/src/ReactNativeAttributePayload.js b/packages/react-native-renderer/src/ReactNativeAttributePayload.js
index fa1187bc339bc..d388f4046a011 100644
--- a/packages/react-native-renderer/src/ReactNativeAttributePayload.js
+++ b/packages/react-native-renderer/src/ReactNativeAttributePayload.js
@@ -12,6 +12,7 @@ import {
   deepDiffer,
   flattenStyle,
 } from 'react-native/Libraries/ReactPrivate/ReactNativePrivateInterface';
+import isArray from 'shared/isArray';
 
 import type {AttributeConfiguration} from './ReactNativeTypes';
 
@@ -51,7 +52,7 @@ function restoreDeletedValuesInNestedArray(
   node: NestedNode,
   validAttributes: AttributeConfiguration,
 ) {
-  if (Array.isArray(node)) {
+  if (isArray(node)) {
     let i = node.length;
     while (i-- && removedKeyCount > 0) {
       restoreDeletedValuesInNestedArray(
@@ -163,12 +164,12 @@ function diffNestedProperty(
     return updatePayload;
   }
 
-  if (!Array.isArray(prevProp) && !Array.isArray(nextProp)) {
+  if (!isArray(prevProp) && !isArray(nextProp)) {
     // Both are leaves, we can diff the leaves.
     return diffProperties(updatePayload, prevProp, nextProp, validAttributes);
   }
 
-  if (Array.isArray(prevProp) && Array.isArray(nextProp)) {
+  if (isArray(prevProp) && isArray(nextProp)) {
     // Both are arrays, we can diff the arrays.
     return diffNestedArrayProperty(
       updatePayload,
@@ -178,7 +179,7 @@ function diffNestedProperty(
     );
   }
 
-  if (Array.isArray(prevProp)) {
+  if (isArray(prevProp)) {
     return diffProperties(
       updatePayload,
       // $FlowFixMe - We know that this is always an object when the input is.
@@ -212,7 +213,7 @@ function addNestedProperty(
     return updatePayload;
   }
 
-  if (!Array.isArray(nextProp)) {
+  if (!isArray(nextProp)) {
     // Add each property of the leaf.
     return addProperties(updatePayload, nextProp, validAttributes);
   }
@@ -242,7 +243,7 @@ function clearNestedProperty(
     return updatePayload;
   }
 
-  if (!Array.isArray(prevProp)) {
+  if (!isArray(prevProp)) {
     // Add each property of the leaf.
     return clearProperties(updatePayload, prevProp, validAttributes);
   }
diff --git a/packages/react-native-renderer/src/__tests__/ReactNativeAttributePayload-test.js b/packages/react-native-renderer/src/__tests__/ReactNativeAttributePayload-test.internal.js
similarity index 100%
rename from packages/react-native-renderer/src/__tests__/ReactNativeAttributePayload-test.js
rename to packages/react-native-renderer/src/__tests__/ReactNativeAttributePayload-test.internal.js
diff --git a/packages/react-native-renderer/src/legacy-events/EventPluginUtils.js b/packages/react-native-renderer/src/legacy-events/EventPluginUtils.js
index abba8e9a3dabe..381ebafc59bb3 100644
--- a/packages/react-native-renderer/src/legacy-events/EventPluginUtils.js
+++ b/packages/react-native-renderer/src/legacy-events/EventPluginUtils.js
@@ -7,6 +7,7 @@
 
 import {invokeGuardedCallbackAndCatchFirstError} from 'shared/ReactErrorUtils';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 
 export let getFiberCurrentPropsFromNode = null;
 export let getInstanceFromNode = null;
@@ -36,14 +37,14 @@ if (__DEV__) {
     const dispatchListeners = event._dispatchListeners;
     const dispatchInstances = event._dispatchInstances;
 
-    const listenersIsArr = Array.isArray(dispatchListeners);
+    const listenersIsArr = isArray(dispatchListeners);
     const listenersLen = listenersIsArr
       ? dispatchListeners.length
       : dispatchListeners
       ? 1
       : 0;
 
-    const instancesIsArr = Array.isArray(dispatchInstances);
+    const instancesIsArr = isArray(dispatchInstances);
     const instancesLen = instancesIsArr
       ? dispatchInstances.length
       : dispatchInstances
@@ -78,7 +79,7 @@ export function executeDispatchesInOrder(event) {
   if (__DEV__) {
     validateEventDispatches(event);
   }
-  if (Array.isArray(dispatchListeners)) {
+  if (isArray(dispatchListeners)) {
     for (let i = 0; i < dispatchListeners.length; i++) {
       if (event.isPropagationStopped()) {
         break;
@@ -106,7 +107,7 @@ function executeDispatchesInOrderStopAtTrueImpl(event) {
   if (__DEV__) {
     validateEventDispatches(event);
   }
-  if (Array.isArray(dispatchListeners)) {
+  if (isArray(dispatchListeners)) {
     for (let i = 0; i < dispatchListeners.length; i++) {
       if (event.isPropagationStopped()) {
         break;
@@ -150,7 +151,7 @@ export function executeDirectDispatch(event) {
   const dispatchListener = event._dispatchListeners;
   const dispatchInstance = event._dispatchInstances;
   invariant(
-    !Array.isArray(dispatchListener),
+    !isArray(dispatchListener),
     'executeDirectDispatch(...): Invalid `event`.',
   );
   event.currentTarget = dispatchListener
diff --git a/packages/react-native-renderer/src/legacy-events/accumulate.js b/packages/react-native-renderer/src/legacy-events/accumulate.js
index 6fcf9f1fd80c0..af4da853934b0 100644
--- a/packages/react-native-renderer/src/legacy-events/accumulate.js
+++ b/packages/react-native-renderer/src/legacy-events/accumulate.js
@@ -8,6 +8,7 @@
  */
 
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 
 /**
  * Accumulates items that must not be null or undefined.
@@ -31,11 +32,11 @@ function accumulate<T>(
 
   // Both are not empty. Warning: Never call x.concat(y) when you are not
   // certain that x is an Array (x could be a string with concat method).
-  if (Array.isArray(current)) {
+  if (isArray(current)) {
     return current.concat(next);
   }
 
-  if (Array.isArray(next)) {
+  if (isArray(next)) {
     return [current].concat(next);
   }
 
diff --git a/packages/react-native-renderer/src/legacy-events/accumulateInto.js b/packages/react-native-renderer/src/legacy-events/accumulateInto.js
index 35625311da88f..d704733d9d455 100644
--- a/packages/react-native-renderer/src/legacy-events/accumulateInto.js
+++ b/packages/react-native-renderer/src/legacy-events/accumulateInto.js
@@ -8,6 +8,7 @@
  */
 
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 
 /**
  * Accumulates items that must not be null or undefined into the first one. This
@@ -37,8 +38,8 @@ function accumulateInto<T>(
 
   // Both are not empty. Warning: Never call x.concat(y) when you are not
   // certain that x is an Array (x could be a string with concat method).
-  if (Array.isArray(current)) {
-    if (Array.isArray(next)) {
+  if (isArray(current)) {
+    if (isArray(next)) {
       current.push.apply(current, next);
       return current;
     }
@@ -46,7 +47,7 @@ function accumulateInto<T>(
     return current;
   }
 
-  if (Array.isArray(next)) {
+  if (isArray(next)) {
     // A bit too dangerous to mutate `next`.
     return [current].concat(next);
   }
diff --git a/packages/react-noop-renderer/src/createReactNoop.js b/packages/react-noop-renderer/src/createReactNoop.js
index ce80ca3374374..9d2c87621bcef 100644
--- a/packages/react-noop-renderer/src/createReactNoop.js
+++ b/packages/react-noop-renderer/src/createReactNoop.js
@@ -21,6 +21,7 @@ import type {RootTag} from 'react-reconciler/src/ReactRootTags';
 
 import * as Scheduler from 'scheduler/unstable_mock';
 import {REACT_FRAGMENT_TYPE, REACT_ELEMENT_TYPE} from 'shared/ReactSymbols';
+import isArray from 'shared/isArray';
 import {
   DefaultEventPriority,
   IdleEventPriority,
@@ -604,7 +605,7 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     if (typeof child === 'string') {
       return child;
     }
-    if (Array.isArray(child)) {
+    if (isArray(child)) {
       if (child.length === 0) {
         return null;
       }
@@ -618,7 +619,7 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
       }
       return children;
     }
-    if (Array.isArray(child.children)) {
+    if (isArray(child.children)) {
       // This is an instance.
       const instance: Instance = (child: any);
       const children = childToJSX(instance.children, instance.text);
@@ -668,7 +669,7 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     if (children === null) {
       return null;
     }
-    if (Array.isArray(children)) {
+    if (isArray(children)) {
       return {
         $$typeof: REACT_ELEMENT_TYPE,
         type: REACT_FRAGMENT_TYPE,
@@ -687,7 +688,7 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     if (children === null) {
       return null;
     }
-    if (Array.isArray(children)) {
+    if (isArray(children)) {
       return {
         $$typeof: REACT_ELEMENT_TYPE,
         type: REACT_FRAGMENT_TYPE,
diff --git a/packages/react-reconciler/src/ReactChildFiber.new.js b/packages/react-reconciler/src/ReactChildFiber.new.js
index f9041ce6590b9..12a693c2d2d7a 100644
--- a/packages/react-reconciler/src/ReactChildFiber.new.js
+++ b/packages/react-reconciler/src/ReactChildFiber.new.js
@@ -31,6 +31,7 @@ import {
   SimpleMemoComponent,
 } from './ReactWorkTags';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {
   warnAboutStringRefs,
   enableLazyElements,
@@ -97,8 +98,6 @@ if (__DEV__) {
   };
 }
 
-const isArray = Array.isArray;
-
 function coerceRef(
   returnFiber: Fiber,
   current: Fiber | null,
diff --git a/packages/react-reconciler/src/ReactChildFiber.old.js b/packages/react-reconciler/src/ReactChildFiber.old.js
index 10c4ccb4dc5be..52d941d19514a 100644
--- a/packages/react-reconciler/src/ReactChildFiber.old.js
+++ b/packages/react-reconciler/src/ReactChildFiber.old.js
@@ -31,6 +31,7 @@ import {
   SimpleMemoComponent,
 } from './ReactWorkTags';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {
   warnAboutStringRefs,
   enableLazyElements,
@@ -97,8 +98,6 @@ if (__DEV__) {
   };
 }
 
-const isArray = Array.isArray;
-
 function coerceRef(
   returnFiber: Fiber,
   current: Fiber | null,
diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.new.js b/packages/react-reconciler/src/ReactFiberBeginWork.new.js
index e707ddf69dfb6..657546a09cdbb 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.new.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.new.js
@@ -87,6 +87,7 @@ import {
   enableSuspenseLayoutEffectSemantics,
 } from 'shared/ReactFeatureFlags';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import shallowEqual from 'shared/shallowEqual';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
@@ -2713,11 +2714,11 @@ function validateTailOptions(
 
 function validateSuspenseListNestedChild(childSlot: mixed, index: number) {
   if (__DEV__) {
-    const isArray = Array.isArray(childSlot);
+    const isAnArray = isArray(childSlot);
     const isIterable =
-      !isArray && typeof getIteratorFn(childSlot) === 'function';
-    if (isArray || isIterable) {
-      const type = isArray ? 'array' : 'iterable';
+      !isAnArray && typeof getIteratorFn(childSlot) === 'function';
+    if (isAnArray || isIterable) {
+      const type = isAnArray ? 'array' : 'iterable';
       console.error(
         'A nested %s was passed to row #%s in <SuspenseList />. Wrap it in ' +
           'an additional SuspenseList to configure its revealOrder: ' +
@@ -2745,7 +2746,7 @@ function validateSuspenseListChildren(
       children !== null &&
       children !== false
     ) {
-      if (Array.isArray(children)) {
+      if (isArray(children)) {
         for (let i = 0; i < children.length; i++) {
           if (!validateSuspenseListNestedChild(children[i], i)) {
             return;
diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.old.js b/packages/react-reconciler/src/ReactFiberBeginWork.old.js
index 10771e018fdb1..f7f8d312803c1 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.old.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.old.js
@@ -87,6 +87,7 @@ import {
   enableSuspenseLayoutEffectSemantics,
 } from 'shared/ReactFeatureFlags';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import shallowEqual from 'shared/shallowEqual';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
@@ -2713,11 +2714,11 @@ function validateTailOptions(
 
 function validateSuspenseListNestedChild(childSlot: mixed, index: number) {
   if (__DEV__) {
-    const isArray = Array.isArray(childSlot);
+    const isAnArray = isArray(childSlot);
     const isIterable =
-      !isArray && typeof getIteratorFn(childSlot) === 'function';
-    if (isArray || isIterable) {
-      const type = isArray ? 'array' : 'iterable';
+      !isAnArray && typeof getIteratorFn(childSlot) === 'function';
+    if (isAnArray || isIterable) {
+      const type = isAnArray ? 'array' : 'iterable';
       console.error(
         'A nested %s was passed to row #%s in <SuspenseList />. Wrap it in ' +
           'an additional SuspenseList to configure its revealOrder: ' +
@@ -2745,7 +2746,7 @@ function validateSuspenseListChildren(
       children !== null &&
       children !== false
     ) {
-      if (Array.isArray(children)) {
+      if (isArray(children)) {
         for (let i = 0; i < children.length; i++) {
           if (!validateSuspenseListNestedChild(children[i], i)) {
             return;
diff --git a/packages/react-reconciler/src/ReactFiberClassComponent.new.js b/packages/react-reconciler/src/ReactFiberClassComponent.new.js
index d64527d58ab65..5aa176a10609b 100644
--- a/packages/react-reconciler/src/ReactFiberClassComponent.new.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.new.js
@@ -36,6 +36,7 @@ import shallowEqual from 'shared/shallowEqual';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {REACT_CONTEXT_TYPE, REACT_PROVIDER_TYPE} from 'shared/ReactSymbols';
 
 import {resolveDefaultProps} from './ReactFiberLazyComponent.new';
@@ -81,7 +82,6 @@ import {
 } from './SchedulingProfiler';
 
 const fakeInternalInstance = {};
-const isArray = Array.isArray;
 
 // React.Component uses a shared frozen object by default.
 // We'll use it to determine whether we need to initialize legacy refs.
diff --git a/packages/react-reconciler/src/ReactFiberClassComponent.old.js b/packages/react-reconciler/src/ReactFiberClassComponent.old.js
index f9b4128b72f76..c4764059baf45 100644
--- a/packages/react-reconciler/src/ReactFiberClassComponent.old.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.old.js
@@ -36,6 +36,7 @@ import shallowEqual from 'shared/shallowEqual';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {REACT_CONTEXT_TYPE, REACT_PROVIDER_TYPE} from 'shared/ReactSymbols';
 
 import {resolveDefaultProps} from './ReactFiberLazyComponent.old';
@@ -81,7 +82,6 @@ import {
 } from './SchedulingProfiler';
 
 const fakeInternalInstance = {};
-const isArray = Array.isArray;
 
 // React.Component uses a shared frozen object by default.
 // We'll use it to determine whether we need to initialize legacy refs.
diff --git a/packages/react-reconciler/src/ReactFiberHooks.new.js b/packages/react-reconciler/src/ReactFiberHooks.new.js
index d5116d1579ecb..5192c6d2740c3 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.new.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.new.js
@@ -87,6 +87,7 @@ import {
 import invariant from 'shared/invariant';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import is from 'shared/objectIs';
+import isArray from 'shared/isArray';
 import {
   markWorkInProgressReceivedUpdate,
   checkIfWorkInProgressReceivedUpdate,
@@ -229,7 +230,7 @@ function updateHookTypesDev() {
 
 function checkDepsAreArrayDev(deps: mixed) {
   if (__DEV__) {
-    if (deps !== undefined && deps !== null && !Array.isArray(deps)) {
+    if (deps !== undefined && deps !== null && !isArray(deps)) {
       // Verify deps, but only on mount to avoid extra checks.
       // It's unlikely their type would change as usually you define them inline.
       console.error(
diff --git a/packages/react-reconciler/src/ReactFiberHooks.old.js b/packages/react-reconciler/src/ReactFiberHooks.old.js
index 77d82bf13c86f..a319cdf75b67c 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.old.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.old.js
@@ -87,6 +87,7 @@ import {
 import invariant from 'shared/invariant';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import is from 'shared/objectIs';
+import isArray from 'shared/isArray';
 import {
   markWorkInProgressReceivedUpdate,
   checkIfWorkInProgressReceivedUpdate,
@@ -229,7 +230,7 @@ function updateHookTypesDev() {
 
 function checkDepsAreArrayDev(deps: mixed) {
   if (__DEV__) {
-    if (deps !== undefined && deps !== null && !Array.isArray(deps)) {
+    if (deps !== undefined && deps !== null && !isArray(deps)) {
       // Verify deps, but only on mount to avoid extra checks.
       // It's unlikely their type would change as usually you define them inline.
       console.error(
diff --git a/packages/react-reconciler/src/ReactFiberReconciler.new.js b/packages/react-reconciler/src/ReactFiberReconciler.new.js
index bbe8810ff52d7..4572e4d9de4ba 100644
--- a/packages/react-reconciler/src/ReactFiberReconciler.new.js
+++ b/packages/react-reconciler/src/ReactFiberReconciler.new.js
@@ -34,6 +34,7 @@ import {
 } from './ReactWorkTags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {enableSchedulingProfiler} from 'shared/ReactFeatureFlags';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 import {getPublicInstance} from './ReactFiberHostConfig';
@@ -482,9 +483,9 @@ if (__DEV__) {
     index: number,
   ) => {
     const key = path[index];
-    const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+    const updated = isArray(obj) ? obj.slice() : {...obj};
     if (index + 1 === path.length) {
-      if (Array.isArray(updated)) {
+      if (isArray(updated)) {
         updated.splice(((key: any): number), 1);
       } else {
         delete updated[key];
@@ -510,12 +511,12 @@ if (__DEV__) {
     index: number,
   ) => {
     const oldKey = oldPath[index];
-    const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+    const updated = isArray(obj) ? obj.slice() : {...obj};
     if (index + 1 === oldPath.length) {
       const newKey = newPath[index];
       // $FlowFixMe number or string is fine here
       updated[newKey] = updated[oldKey];
-      if (Array.isArray(updated)) {
+      if (isArray(updated)) {
         updated.splice(((oldKey: any): number), 1);
       } else {
         delete updated[oldKey];
@@ -564,7 +565,7 @@ if (__DEV__) {
       return value;
     }
     const key = path[index];
-    const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+    const updated = isArray(obj) ? obj.slice() : {...obj};
     // $FlowFixMe number or string is fine here
     updated[key] = copyWithSetImpl(obj[key], path, index + 1, value);
     return updated;
diff --git a/packages/react-reconciler/src/ReactFiberReconciler.old.js b/packages/react-reconciler/src/ReactFiberReconciler.old.js
index c6ced2f5be5b6..abd5b9094c59c 100644
--- a/packages/react-reconciler/src/ReactFiberReconciler.old.js
+++ b/packages/react-reconciler/src/ReactFiberReconciler.old.js
@@ -34,6 +34,7 @@ import {
 } from './ReactWorkTags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {enableSchedulingProfiler} from 'shared/ReactFeatureFlags';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 import {getPublicInstance} from './ReactFiberHostConfig';
@@ -482,9 +483,9 @@ if (__DEV__) {
     index: number,
   ) => {
     const key = path[index];
-    const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+    const updated = isArray(obj) ? obj.slice() : {...obj};
     if (index + 1 === path.length) {
-      if (Array.isArray(updated)) {
+      if (isArray(updated)) {
         updated.splice(((key: any): number), 1);
       } else {
         delete updated[key];
@@ -510,12 +511,12 @@ if (__DEV__) {
     index: number,
   ) => {
     const oldKey = oldPath[index];
-    const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+    const updated = isArray(obj) ? obj.slice() : {...obj};
     if (index + 1 === oldPath.length) {
       const newKey = newPath[index];
       // $FlowFixMe number or string is fine here
       updated[newKey] = updated[oldKey];
-      if (Array.isArray(updated)) {
+      if (isArray(updated)) {
         updated.splice(((oldKey: any): number), 1);
       } else {
         delete updated[oldKey];
@@ -564,7 +565,7 @@ if (__DEV__) {
       return value;
     }
     const key = path[index];
-    const updated = Array.isArray(obj) ? obj.slice() : {...obj};
+    const updated = isArray(obj) ? obj.slice() : {...obj};
     // $FlowFixMe number or string is fine here
     updated[key] = copyWithSetImpl(obj[key], path, index + 1, value);
     return updated;
diff --git a/packages/react-server-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js b/packages/react-server-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js
index 09dd7df1d5533..35203ee92c5c5 100644
--- a/packages/react-server-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js
+++ b/packages/react-server-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js
@@ -24,6 +24,8 @@ export {
   requireModule,
 } from 'ReactFlightDOMRelayClientIntegration';
 
+import isArray from 'shared/isArray';
+
 export type {ModuleMetaData} from 'ReactFlightDOMRelayClientIntegration';
 
 export type UninitializedModel = JSONValue;
@@ -35,7 +37,7 @@ function parseModelRecursively(response: Response, parentObj, value) {
     return parseModelString(response, parentObj, value);
   }
   if (typeof value === 'object' && value !== null) {
-    if (Array.isArray(value)) {
+    if (isArray(value)) {
       const parsedValue = [];
       for (let i = 0; i < value.length; i++) {
         (parsedValue: any)[i] = parseModelRecursively(
diff --git a/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js b/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
index a4d0d26fcce14..85eace536ac4e 100644
--- a/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
+++ b/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
@@ -14,6 +14,7 @@ import type {Request, ReactModel} from 'react-server/src/ReactFlightServer';
 import JSResourceReference from 'JSResourceReference';
 
 import hasOwnProperty from 'shared/hasOwnProperty';
+import isArray from 'shared/isArray';
 
 export type ModuleReference<T> = JSResourceReference<T>;
 
@@ -82,7 +83,7 @@ function convertModelToJSON(
 ): JSONValue {
   const json = resolveModelToJSON(request, parent, key, model);
   if (typeof json === 'object' && json !== null) {
-    if (Array.isArray(json)) {
+    if (isArray(json)) {
       const jsonArray: Array<JSONValue> = [];
       for (let i = 0; i < json.length; i++) {
         jsonArray[i] = convertModelToJSON(request, json, '' + i, json[i]);
diff --git a/packages/react-server-dom-webpack/src/ReactFlightWebpackPlugin.js b/packages/react-server-dom-webpack/src/ReactFlightWebpackPlugin.js
index ecdd66ed82c66..a81aec2c17384 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightWebpackPlugin.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightWebpackPlugin.js
@@ -17,6 +17,8 @@ import NullDependency from 'webpack/lib/dependencies/NullDependency';
 import AsyncDependenciesBlock from 'webpack/lib/AsyncDependenciesBlock';
 import Template from 'webpack/lib/Template';
 
+import isArray from 'shared/isArray';
+
 class ClientReferenceDependency extends ModuleDependency {
   constructor(request) {
     super(request);
@@ -76,7 +78,7 @@ export default class ReactFlightWebpackPlugin {
       ];
     } else if (
       typeof options.clientReferences === 'string' ||
-      !Array.isArray(options.clientReferences)
+      !isArray(options.clientReferences)
     ) {
       this.clientReferences = [(options.clientReferences: $FlowFixMe)];
     } else {
diff --git a/packages/react-server-native-relay/src/ReactFlightNativeRelayClientHostConfig.js b/packages/react-server-native-relay/src/ReactFlightNativeRelayClientHostConfig.js
index 7ff02159bb7ef..d8e27657b2925 100644
--- a/packages/react-server-native-relay/src/ReactFlightNativeRelayClientHostConfig.js
+++ b/packages/react-server-native-relay/src/ReactFlightNativeRelayClientHostConfig.js
@@ -24,6 +24,8 @@ export {
   requireModule,
 } from 'ReactFlightNativeRelayClientIntegration';
 
+import isArray from 'shared/isArray';
+
 export type {ModuleMetaData} from 'ReactFlightNativeRelayClientIntegration';
 
 export type UninitializedModel = JSONValue;
@@ -35,7 +37,7 @@ function parseModelRecursively(response: Response, parentObj, value) {
     return parseModelString(response, parentObj, value);
   }
   if (typeof value === 'object' && value !== null) {
-    if (Array.isArray(value)) {
+    if (isArray(value)) {
       const parsedValue = [];
       for (let i = 0; i < value.length; i++) {
         (parsedValue: any)[i] = parseModelRecursively(
diff --git a/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js b/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
index 4fa871b0c4e8f..0624e693cfe16 100644
--- a/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
+++ b/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
@@ -8,9 +8,9 @@
  */
 
 import type {RowEncoding, JSONValue} from './ReactFlightNativeRelayProtocol';
-
 import type {Request, ReactModel} from 'react-server/src/ReactFlightServer';
 import hasOwnProperty from 'shared/hasOwnProperty';
+import isArray from 'shared/isArray';
 import JSResourceReferenceImpl from 'JSResourceReferenceImpl';
 
 export type ModuleReference<T> = JSResourceReferenceImpl<T>;
@@ -80,7 +80,7 @@ function convertModelToJSON(
 ): JSONValue {
   const json = resolveModelToJSON(request, parent, key, model);
   if (typeof json === 'object' && json !== null) {
-    if (Array.isArray(json)) {
+    if (isArray(json)) {
       const jsonArray: Array<JSONValue> = [];
       for (let i = 0; i < json.length; i++) {
         jsonArray[i] = convertModelToJSON(request, json, '' + i, json[i]);
diff --git a/packages/react-server/src/ReactFizzServer.js b/packages/react-server/src/ReactFizzServer.js
index 66a6c9238ab30..75beaf0f219bf 100644
--- a/packages/react-server/src/ReactFizzServer.js
+++ b/packages/react-server/src/ReactFizzServer.js
@@ -51,6 +51,7 @@ import {REACT_ELEMENT_TYPE, REACT_SUSPENSE_TYPE} from 'shared/ReactSymbols';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 
 const ReactCurrentDispatcher = ReactSharedInternals.ReactCurrentDispatcher;
 
@@ -287,7 +288,7 @@ function renderNode(request: Request, task: Task, node: ReactNodeList): void {
     return;
   }
 
-  if (Array.isArray(node)) {
+  if (isArray(node)) {
     if (node.length > 0) {
       for (let i = 0; i < node.length; i++) {
         renderNode(request, task, node[i]);
diff --git a/packages/react-server/src/ReactFlightServer.js b/packages/react-server/src/ReactFlightServer.js
index dfbe3c55f9b64..58c3a9219f644 100644
--- a/packages/react-server/src/ReactFlightServer.js
+++ b/packages/react-server/src/ReactFlightServer.js
@@ -44,8 +44,7 @@ import {
 
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 import invariant from 'shared/invariant';
-
-const isArray = Array.isArray;
+import isArray from 'shared/isArray';
 
 type ReactJSONValue =
   | string
diff --git a/packages/react-test-renderer/src/ReactTestHostConfig.js b/packages/react-test-renderer/src/ReactTestHostConfig.js
index 596615ea05705..6cdadabe281a5 100644
--- a/packages/react-test-renderer/src/ReactTestHostConfig.js
+++ b/packages/react-test-renderer/src/ReactTestHostConfig.js
@@ -8,6 +8,7 @@
  */
 
 import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
+import isArray from 'shared/isArray';
 import {DefaultEventPriority} from 'react-reconciler/src/ReactEventPriorities';
 
 export type Type = string;
@@ -84,7 +85,7 @@ export function appendChild(
   child: Instance | TextInstance,
 ): void {
   if (__DEV__) {
-    if (!Array.isArray(parentInstance.children)) {
+    if (!isArray(parentInstance.children)) {
       console.error(
         'An invalid container has been provided. ' +
           'This may indicate that another renderer is being used in addition to the test renderer. ' +
diff --git a/packages/react-test-renderer/src/ReactTestRenderer.js b/packages/react-test-renderer/src/ReactTestRenderer.js
index f058af3e87584..5c74c6e9e310c 100644
--- a/packages/react-test-renderer/src/ReactTestRenderer.js
+++ b/packages/react-test-renderer/src/ReactTestRenderer.js
@@ -43,6 +43,7 @@ import {
   ScopeComponent,
 } from 'react-reconciler/src/ReactWorkTags';
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 import ReactVersion from 'shared/ReactVersion';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
@@ -158,7 +159,7 @@ function flatten(arr) {
     while (n.i < n.array.length) {
       const el = n.array[n.i];
       n.i += 1;
-      if (Array.isArray(el)) {
+      if (isArray(el)) {
         stack.push(n);
         stack.push({i: 0, array: el});
         break;
diff --git a/packages/react/src/ReactChildren.js b/packages/react/src/ReactChildren.js
index eb9ef5aca9ca7..9acdc068e8ea3 100644
--- a/packages/react/src/ReactChildren.js
+++ b/packages/react/src/ReactChildren.js
@@ -10,6 +10,7 @@
 import type {ReactNodeList} from 'shared/ReactTypes';
 
 import invariant from 'shared/invariant';
+import isArray from 'shared/isArray';
 import {
   getIteratorFn,
   REACT_ELEMENT_TYPE,
@@ -110,7 +111,7 @@ function mapIntoArray(
     // so that it's consistent if the number of children grows:
     const childKey =
       nameSoFar === '' ? SEPARATOR + getElementKey(child, 0) : nameSoFar;
-    if (Array.isArray(mappedChild)) {
+    if (isArray(mappedChild)) {
       let escapedChildKey = '';
       if (childKey != null) {
         escapedChildKey = escapeUserProvidedKey(childKey) + '/';
@@ -142,7 +143,7 @@ function mapIntoArray(
   const nextNamePrefix =
     nameSoFar === '' ? SEPARATOR : nameSoFar + SUBSEPARATOR;
 
-  if (Array.isArray(children)) {
+  if (isArray(children)) {
     for (let i = 0; i < children.length; i++) {
       child = children[i];
       nextName = nextNamePrefix + getElementKey(child, i);
diff --git a/packages/react/src/ReactElementValidator.js b/packages/react/src/ReactElementValidator.js
index 2c14bef6c0201..f9d2cbb95af14 100644
--- a/packages/react/src/ReactElementValidator.js
+++ b/packages/react/src/ReactElementValidator.js
@@ -23,6 +23,7 @@ import {
 } from 'shared/ReactSymbols';
 import {warnAboutSpreadingKeyToJSX} from 'shared/ReactFeatureFlags';
 import checkPropTypes from 'shared/checkPropTypes';
+import isArray from 'shared/isArray';
 
 import ReactCurrentOwner from './ReactCurrentOwner';
 import {
@@ -168,7 +169,7 @@ function validateChildKeys(node, parentType) {
   if (typeof node !== 'object') {
     return;
   }
-  if (Array.isArray(node)) {
+  if (isArray(node)) {
     for (let i = 0; i < node.length; i++) {
       const child = node[i];
       if (isValidElement(child)) {
@@ -313,7 +314,7 @@ export function jsxWithValidation(
     let typeString;
     if (type === null) {
       typeString = 'null';
-    } else if (Array.isArray(type)) {
+    } else if (isArray(type)) {
       typeString = 'array';
     } else if (type !== undefined && type.$$typeof === REACT_ELEMENT_TYPE) {
       typeString = `<${getComponentNameFromType(type.type) || 'Unknown'} />`;
@@ -352,7 +353,7 @@ export function jsxWithValidation(
     const children = props.children;
     if (children !== undefined) {
       if (isStaticChildren) {
-        if (Array.isArray(children)) {
+        if (isArray(children)) {
           for (let i = 0; i < children.length; i++) {
             validateChildKeys(children[i], type);
           }
@@ -437,7 +438,7 @@ export function createElementWithValidation(type, props, children) {
     let typeString;
     if (type === null) {
       typeString = 'null';
-    } else if (Array.isArray(type)) {
+    } else if (isArray(type)) {
       typeString = 'array';
     } else if (type !== undefined && type.$$typeof === REACT_ELEMENT_TYPE) {
       typeString = `<${getComponentNameFromType(type.type) || 'Unknown'} />`;
diff --git a/packages/react/src/jsx/ReactJSXElementValidator.js b/packages/react/src/jsx/ReactJSXElementValidator.js
index c77b5ef6e9a6f..84cf3eb2caa3b 100644
--- a/packages/react/src/jsx/ReactJSXElementValidator.js
+++ b/packages/react/src/jsx/ReactJSXElementValidator.js
@@ -23,6 +23,7 @@ import {
 } from 'shared/ReactSymbols';
 import {warnAboutSpreadingKeyToJSX} from 'shared/ReactFeatureFlags';
 import hasOwnProperty from 'shared/hasOwnProperty';
+import isArray from 'shared/isArray';
 import {jsxDEV} from './ReactJSXElement';
 
 import {describeUnknownElementTypeFrameInDEV} from 'shared/ReactComponentStackFrame';
@@ -182,7 +183,7 @@ function validateChildKeys(node, parentType) {
     if (typeof node !== 'object') {
       return;
     }
-    if (Array.isArray(node)) {
+    if (isArray(node)) {
       for (let i = 0; i < node.length; i++) {
         const child = node[i];
         if (isValidElement(child)) {
@@ -329,7 +330,7 @@ export function jsxWithValidation(
       let typeString;
       if (type === null) {
         typeString = 'null';
-      } else if (Array.isArray(type)) {
+      } else if (isArray(type)) {
         typeString = 'array';
       } else if (type !== undefined && type.$$typeof === REACT_ELEMENT_TYPE) {
         typeString = `<${getComponentNameFromType(type.type) || 'Unknown'} />`;
@@ -366,7 +367,7 @@ export function jsxWithValidation(
       const children = props.children;
       if (children !== undefined) {
         if (isStaticChildren) {
-          if (Array.isArray(children)) {
+          if (isArray(children)) {
             for (let i = 0; i < children.length; i++) {
               validateChildKeys(children[i], type);
             }
diff --git a/packages/shared/isArray.js b/packages/shared/isArray.js
new file mode 100644
index 0000000000000..53fb7710bb3c4
--- /dev/null
+++ b/packages/shared/isArray.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+declare function isArray(a: mixed): boolean %checks(Array.isArray(a));
+
+const isArrayImpl = Array.isArray;
+
+// eslint-disable-next-line no-redeclare
+function isArray(a: mixed): boolean {
+  return isArrayImpl(a);
+}
+
+export default isArray;