Remove var in RNTester (#22014)

Summary:
I removed `var` in RNTester.

- [x] npm run prettier
- [x] npm run flow-check-ios
- [x] npm run flow-check-android

[GENERAL] [ENHANCEMENT] [RNTester] - remove `var`
Pull Request resolved: facebook/react-native#22014

Differential Revision: D12843150

Pulled By: TheSavior

fbshipit-source-id: 593adf141164cffe0ddc2db756721df26e38b4f5

ViewPagerAndroidExample.android.js

@@ -9,9 +9,9 @@
 
 'use strict';
 
-var React = require('react');
-var ReactNative = require('react-native');
-var {
+const React = require('react');
+const ReactNative = require('react-native');
+const {
   Image,
   StyleSheet,
   Text,
@@ -23,9 +23,9 @@ var {
 
 import type {ViewPagerScrollState} from 'ViewPagerAndroid';
 
-var PAGES = 5;
-var BGCOLOR = ['#fdc08e', '#fff6b9', '#99d1b7', '#dde5fe', '#f79273'];
-var IMAGE_URIS = [
+const PAGES = 5;
+const BGCOLOR = ['#fdc08e', '#fff6b9', '#99d1b7', '#dde5fe', '#f79273'];
+const IMAGE_URIS = [
   'https://apod.nasa.gov/apod/image/1410/20141008tleBaldridge001h990.jpg',
   'https://apod.nasa.gov/apod/image/1409/volcanicpillar_vetter_960.jpg',
   'https://apod.nasa.gov/apod/image/1409/m27_snyder_960.jpg',
@@ -43,7 +43,7 @@ class LikeCount extends React.Component {
   };
 
   render() {
-    var thumbsUp = '\uD83D\uDC4D';
+    const thumbsUp = '\uD83D\uDC4D';
     return (
       <View style={styles.likeContainer}>
         <TouchableOpacity onPress={this.onClick} style={styles.likeButton}>
@@ -79,9 +79,10 @@ class Button extends React.Component {
 
 class ProgressBar extends React.Component {
   render() {
-    var fractionalPosition =
+    const fractionalPosition =
       this.props.progress.position + this.props.progress.offset;
-    var progressBarSize = (fractionalPosition / (PAGES - 1)) * this.props.size;
+    const progressBarSize =
+      (fractionalPosition / (PAGES - 1)) * this.props.size;
     return (
       <View style={[styles.progressBarContainer, {width: this.props.size}]}>
         <View style={[styles.progressBar, {width: progressBarSize}]} />
@@ -118,7 +119,7 @@ class ViewPagerAndroidExample extends React.Component {
   };
 
   move = delta => {
-    var page = this.state.page + delta;
+    const page = this.state.page + delta;
     this.go(page);
   };
 
@@ -133,9 +134,9 @@ class ViewPagerAndroidExample extends React.Component {
   };
 
   render() {
-    var pages = [];
-    for (var i = 0; i < PAGES; i++) {
-      var pageStyle = {
+    const pages = [];
+    for (let i = 0; i < PAGES; i++) {
+      const pageStyle = {
         backgroundColor: BGCOLOR[i % BGCOLOR.length],
         alignItems: 'center',
         padding: 20,
@@ -150,7 +151,7 @@ class ViewPagerAndroidExample extends React.Component {
         </View>,
       );
     }
-    var {page, animationsAreEnabled} = this.state;
+    const {page, animationsAreEnabled} = this.state;
     return (
       <View style={styles.container}>
         <ViewPagerAndroid
@@ -222,7 +223,7 @@ class ViewPagerAndroidExample extends React.Component {
   }
 }
 
-var styles = StyleSheet.create({
+const styles = StyleSheet.create({
   buttons: {
     flexDirection: 'row',
     height: 30,