react: convert var to let/const (#11715)

Author: raphamorim

packages/react/index.js

@@ -9,7 +9,7 @@
 
 'use strict';
 
-var React = require('./src/React');
+const React = require('./src/React');
 
 // TODO: decide on the top-level export form.
 // This is hacky but makes it work with both Rollup and Jest.

packages/react/src/React.js

@@ -25,7 +25,7 @@ import {
 } from './ReactElementValidator';
 import ReactDebugCurrentFrame from './ReactDebugCurrentFrame';
 
-var React = {
+const React = {
   Children: {
     map,
     forEach,

packages/react/src/ReactBaseClasses.js

@@ -85,7 +85,7 @@ Component.prototype.forceUpdate = function(callback) {
  * modern base class. Instead, we define a getter that warns if it's accessed.
  */
 if (__DEV__) {
-  var deprecatedAPIs = {
+  const deprecatedAPIs = {
     isMounted: [
       'isMounted',
       'Instead, make sure to clean up subscriptions and pending requests in ' +
@@ -97,7 +97,7 @@ if (__DEV__) {
         'https://github.com/facebook/react/issues/3236).',
     ],
   };
-  var defineDeprecationWarning = function(methodName, info) {
+  const defineDeprecationWarning = function(methodName, info) {
     Object.defineProperty(Component.prototype, methodName, {
       get: function() {
         lowPriorityWarning(
@@ -110,7 +110,7 @@ if (__DEV__) {
       },
     });
   };
-  for (var fnName in deprecatedAPIs) {
+  for (const fnName in deprecatedAPIs) {
     if (deprecatedAPIs.hasOwnProperty(fnName)) {
       defineDeprecationWarning(fnName, deprecatedAPIs[fnName]);
     }
@@ -132,7 +132,7 @@ function PureComponent(props, context, updater) {
 
 function ComponentDummy() {}
 ComponentDummy.prototype = Component.prototype;
-var pureComponentPrototype = (PureComponent.prototype = new ComponentDummy());
+const pureComponentPrototype = (PureComponent.prototype = new ComponentDummy());
 pureComponentPrototype.constructor = PureComponent;
 // Avoid an extra prototype jump for these methods.
 Object.assign(pureComponentPrototype, Component.prototype);
@@ -148,7 +148,7 @@ function AsyncComponent(props, context, updater) {
   this.updater = updater || ReactNoopUpdateQueue;
 }
 
-var asyncComponentPrototype = (AsyncComponent.prototype = new ComponentDummy());
+const asyncComponentPrototype = (AsyncComponent.prototype = new ComponentDummy());
 asyncComponentPrototype.constructor = AsyncComponent;
 // Avoid an extra prototype jump for these methods.
 Object.assign(asyncComponentPrototype, Component.prototype);

packages/react/src/ReactChildren.js

@@ -19,8 +19,8 @@ import {
 import {isValidElement, cloneAndReplaceKey} from './ReactElement';
 import ReactDebugCurrentFrame from './ReactDebugCurrentFrame';
 
-var SEPARATOR = '.';
-var SUBSEPARATOR = ':';
+const SEPARATOR = '.';
+const SUBSEPARATOR = ':';
 
 /**
  * Escape and wrap key so it is safe to use as a reactid
@@ -29,12 +29,12 @@ var SUBSEPARATOR = ':';
  * @return {string} the escaped key.
  */
 function escape(key) {
-  var escapeRegex = /[=:]/g;
-  var escaperLookup = {
+  const escapeRegex = /[=:]/g;
+  const escaperLookup = {
     '=': '=0',
     ':': '=2',
   };
-  var escapedString = ('' + key).replace(escapeRegex, function(match) {
+  const escapedString = ('' + key).replace(escapeRegex, function(match) {
     return escaperLookup[match];
   });
 
@@ -46,23 +46,23 @@ function escape(key) {
  * pattern.
  */
 
-var didWarnAboutMaps = false;
+let didWarnAboutMaps = false;
 
-var userProvidedKeyEscapeRegex = /\/+/g;
+const userProvidedKeyEscapeRegex = /\/+/g;
 function escapeUserProvidedKey(text) {
   return ('' + text).replace(userProvidedKeyEscapeRegex, '$&/');
 }
 
-var POOL_SIZE = 10;
-var traverseContextPool = [];
+const POOL_SIZE = 10;
+const traverseContextPool = [];
 function getPooledTraverseContext(
   mapResult,
   keyPrefix,
   mapFunction,
   mapContext,
 ) {
   if (traverseContextPool.length) {
-    var traverseContext = traverseContextPool.pop();
+    const traverseContext = traverseContextPool.pop();
     traverseContext.result = mapResult;
     traverseContext.keyPrefix = keyPrefix;
     traverseContext.func = mapFunction;
@@ -105,7 +105,7 @@ function traverseAllChildrenImpl(
   callback,
   traverseContext,
 ) {
-  var type = typeof children;
+  const type = typeof children;
 
   if (type === 'undefined' || type === 'boolean') {
     // All of the above are perceived as null.
@@ -144,13 +144,14 @@ function traverseAllChildrenImpl(
     return 1;
   }
 
-  var child;
-  var nextName;
-  var subtreeCount = 0; // Count of children found in the current subtree.
-  var nextNamePrefix = nameSoFar === '' ? SEPARATOR : nameSoFar + SUBSEPARATOR;
+  let child;
+  let nextName;
+  let subtreeCount = 0; // Count of children found in the current subtree.
+  const nextNamePrefix =
+    nameSoFar === '' ? SEPARATOR : nameSoFar + SUBSEPARATOR;
 
   if (Array.isArray(children)) {
-    for (var i = 0; i < children.length; i++) {
+    for (let i = 0; i < children.length; i++) {
       child = children[i];
       nextName = nextNamePrefix + getComponentKey(child, i);
       subtreeCount += traverseAllChildrenImpl(
@@ -161,7 +162,7 @@ function traverseAllChildrenImpl(
       );
     }
   } else {
-    var iteratorFn = getIteratorFn(children);
+    const iteratorFn = getIteratorFn(children);
     if (typeof iteratorFn === 'function') {
       if (__DEV__) {
         // Warn about using Maps as children
@@ -177,9 +178,9 @@ function traverseAllChildrenImpl(
         }
       }
 
-      var iterator = iteratorFn.call(children);
-      var step;
-      var ii = 0;
+      const iterator = iteratorFn.call(children);
+      let step;
+      let ii = 0;
       while (!(step = iterator.next()).done) {
         child = step.value;
         nextName = nextNamePrefix + getComponentKey(child, ii++);
@@ -191,14 +192,14 @@ function traverseAllChildrenImpl(
         );
       }
     } else if (type === 'object') {
-      var addendum = '';
+      let addendum = '';
       if (__DEV__) {
         addendum =
           ' If you meant to render a collection of children, use an array ' +
           'instead.' +
           ReactDebugCurrentFrame.getStackAddendum();
       }
-      var childrenString = '' + children;
+      const childrenString = '' + children;
       invariant(
         false,
         'Objects are not valid as a React child (found: %s).%s',
@@ -260,7 +261,7 @@ function getComponentKey(component, index) {
 }
 
 function forEachSingleChild(bookKeeping, child, name) {
-  var {func, context} = bookKeeping;
+  const {func, context} = bookKeeping;
   func.call(context, child, bookKeeping.count++);
 }
 
@@ -280,7 +281,7 @@ function forEachChildren(children, forEachFunc, forEachContext) {
   if (children == null) {
     return children;
   }
-  var traverseContext = getPooledTraverseContext(
+  const traverseContext = getPooledTraverseContext(
     null,
     null,
     forEachFunc,
@@ -291,9 +292,9 @@ function forEachChildren(children, forEachFunc, forEachContext) {
 }
 
 function mapSingleChildIntoContext(bookKeeping, child, childKey) {
-  var {result, keyPrefix, func, context} = bookKeeping;
+  const {result, keyPrefix, func, context} = bookKeeping;
 
-  var mappedChild = func.call(context, child, bookKeeping.count++);
+  let mappedChild = func.call(context, child, bookKeeping.count++);
   if (Array.isArray(mappedChild)) {
     mapIntoWithKeyPrefixInternal(
       mappedChild,
@@ -319,11 +320,11 @@ function mapSingleChildIntoContext(bookKeeping, child, childKey) {
 }
 
 function mapIntoWithKeyPrefixInternal(children, array, prefix, func, context) {
-  var escapedPrefix = '';
+  let escapedPrefix = '';
   if (prefix != null) {
     escapedPrefix = escapeUserProvidedKey(prefix) + '/';
   }
-  var traverseContext = getPooledTraverseContext(
+  const traverseContext = getPooledTraverseContext(
     array,
     escapedPrefix,
     func,
@@ -350,7 +351,7 @@ function mapChildren(children, func, context) {
   if (children == null) {
     return children;
   }
-  var result = [];
+  const result = [];
   mapIntoWithKeyPrefixInternal(children, result, null, func, context);
   return result;
 }
@@ -375,7 +376,7 @@ function countChildren(children, context) {
  * See https://reactjs.org/docs/react-api.html#react.children.toarray
  */
 function toArray(children) {
-  var result = [];
+  const result = [];
   mapIntoWithKeyPrefixInternal(
     children,
     result,

packages/react/src/ReactCurrentOwner.js

@@ -15,7 +15,7 @@ import type {Fiber} from 'react-reconciler/src/ReactFiber';
  * The current owner is the component who should own any components that are
  * currently being constructed.
  */
-var ReactCurrentOwner = {
+const ReactCurrentOwner = {
   /**
    * @internal
    * @type {ReactComponent}