Navigator: Improve backward compatibility of scripts

CHANGELOG.md

@@ -37,6 +37,7 @@ All notable changes to this project will be documented in this file. Take a look
 * Fixed turning pages of an EPUB reflowable resource with an odd number of columns. A virtual blank trailing column is appended to the resource when displayed as two columns.
 * EPUB: Fallback on `reflowable` if the `presentation.layout` hint is missing from a manifest.
 * EPUB: Offset of the current selection's `rect` to take into account the vertical padding.
+* Improve backward compatibility of JavaScript files using Babel.
 
 
 ## [2.1.1]

readium/navigator/src/main/assets/_scripts/.eslintrc.json

@@ -5,6 +5,7 @@
     },
     "globals": {
         "Android": "readonly",
+        "global": "writable",
         "readium": "writable"
     },
     "extends": "eslint:recommended",

readium/navigator/src/main/assets/_scripts/babel.config.json

@@ -0,0 +1,3 @@
+{
+      "presets": ["@babel/preset-env"]
+}

readium/navigator/src/main/assets/_scripts/package.json

@@ -1,6 +1,8 @@
 {
   "name": "readium-js",
+  "author": "Readium Foundation",
   "version": "0.1.0",
+  "license": "BSD-3-Clause",
   "description": "A set of scripts for the EPUB navigator",
   "private": true,
   "scripts": {
@@ -9,9 +11,11 @@
     "checkformat": "prettier --check '**/*.js'",
     "format": "prettier --list-different --write '**/*.js'"
   },
-  "author": "Readium Foundation",
-  "license": "BSD-3-Clause",
+  "browserslist": [ "Android >= 4" ],
   "devDependencies": {
+    "@babel/core": "^7.16.0",
+    "@babel/preset-env": "^7.16.0",
+    "babel-loader": "^8.2.3",
     "eslint": "^7.29.0",
     "prettier": "2.3.1",
     "webpack": "^5.40.0",

readium/navigator/src/main/assets/_scripts/webpack.config.js

@@ -11,4 +11,18 @@ module.exports = {
     filename: "readium-[name].js",
     path: path.resolve(__dirname, "../readium/scripts"),
   },
+  module: {
+    rules: [
+      {
+        test: /\.m?js$/,
+        exclude: /node_modules/,
+        use: {
+          loader: "babel-loader",
+          options: {
+            presets: ["@babel/preset-env"],
+          },
+        },
+      },
+    ],
+  },
 };

readium/navigator/src/main/assets/readium/scripts/.gitignore

@@ -0,0 +1 @@
+*.map