Improve code style of examples.

Consts are preferable because readers don't have to think about potential
future code paths affecting the value.

Author: DylanVann

example/FastImageExample.js

@@ -8,24 +8,29 @@ import uuid from 'uuid/v4'
 
 const getImageUrl = (id, width, height) =>
   `https://source.unsplash.com/${id}/${width}x${height}`
-let IMAGE_1
-let IMAGE_2
-let IMAGE_3
+
 const IMAGE_SIZE = 150
 const USE_SERVER = false
-const token = 'someToken'
-if (USE_SERVER) {
-  const baseUrl = '192.168.2.11'
-  IMAGE_1 = `http://${baseUrl}:8080/pictures/ahmed-saffu-235616.jpg`
-  IMAGE_2 = `http://${baseUrl}:8080/pictures/alex-bertha-236361.jpg`
-  IMAGE_3 = `http://${baseUrl}:8080/pictures/jaromir-kavan-233699.jpg`
-} else {
-  IMAGE_1 = getImageUrl('x58soEovG_M', IMAGE_SIZE, IMAGE_SIZE)
-  IMAGE_2 = getImageUrl('yPI7myL5eWY', IMAGE_SIZE, IMAGE_SIZE)
-  IMAGE_3 =
-    'https://cdn-images-1.medium.com/max/1600/1*-CY5bU4OqiJRox7G00sftw.gif'
+const TOKEN = 'someToken'
+
+const getImages = () => {
+  if (USE_SERVER) {
+    const baseUrl = '192.168.2.11'
+    return [
+      `http://${baseUrl}:8080/pictures/ahmed-saffu-235616.jpg`,
+      `http://${baseUrl}:8080/pictures/alex-bertha-236361.jpg`,
+      `http://${baseUrl}:8080/pictures/jaromir-kavan-233699.jpg`,
+    ]
+  }
+  return [
+    getImageUrl('x58soEovG_M', IMAGE_SIZE, IMAGE_SIZE),
+    getImageUrl('yPI7myL5eWY', IMAGE_SIZE, IMAGE_SIZE),
+    'https://cdn-images-1.medium.com/max/1600/1*-CY5bU4OqiJRox7G00sftw.gif',
+  ]
 }
 
+const images = getImages()
+
 class FastImageExample extends Component {
   componentDidMount() {
     // Forcing an update every 5s to demonstrate loading.
@@ -58,29 +63,29 @@ class FastImageExample extends Component {
           <FastImage
             style={styles.image}
             source={{
-              uri: IMAGE_1 + bust,
+              uri: images[0] + bust,
               headers: {
-                token,
+                token: TOKEN,
               },
               priority: FastImage.priority.low,
             }}
           />
           <FastImage
             style={styles.image}
             source={{
-              uri: IMAGE_2 + bust,
+              uri: images[1] + bust,
               headers: {
-                token,
+                token: TOKEN,
               },
               priority: FastImage.priority.normal,
             }}
           />
           <FastImage
             style={styles.image}
             source={{
-              uri: IMAGE_3 + bust,
+              uri: images[2] + bust,
               headers: {
-                token,
+                token: TOKEN,
               },
               priority: FastImage.priority.high,
             }}