Remove redundant initial of isArray (#21163)

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]) {
@@ -255,7 +257,7 @@ export default {
         } else if (name === 'useTransition') {
           if (
             id.type === 'ArrayPattern' &&
-            Array.isArray(resolved.identifiers)
+            isArray(resolved.identifiers)
           ) {
             // Is first tuple value the same reference we're checking?
             if (id.elements[0] === resolved.identifiers[0]) {
@@ -270,7 +272,7 @@ 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];

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) {

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')
     );
   }

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;

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',

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.',

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 = {

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) {

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;

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);
   }

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

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);
   }
 

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);
   }

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,

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,

packages/react-reconciler/src/ReactChildFiber.old.js

@@ -11,6 +11,7 @@ import type {ReactElement} from 'shared/ReactElementType';
 import type {ReactPortal} from 'shared/ReactTypes';
 import type {Fiber} from './ReactInternalTypes';
 import type {Lanes} from './ReactFiberLane.old';
+import isArray from 'shared/isArray';
 
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 import {Placement, ChildDeletion} from './ReactFiberFlags';
@@ -97,8 +98,6 @@ if (__DEV__) {
   };
 }
 
-const isArray = Array.isArray;
-
 function coerceRef(
   returnFiber: Fiber,
   current: Fiber | null,

packages/react-reconciler/src/ReactFiberClassComponent.new.js

@@ -29,6 +29,7 @@ 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';
@@ -74,7 +75,6 @@ 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.

packages/react-reconciler/src/ReactFiberClassComponent.old.js

@@ -29,6 +29,7 @@ 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';
@@ -74,7 +75,6 @@ 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.

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;

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;

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]);

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]);

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]);

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

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);

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'} />`;

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);
             }

packages/shared/isArray.js

@@ -0,0 +1,12 @@
+/**
+ * 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
+ */
+
+const isArray = Array.isArray;
+
+export default isArray;