Add ESLint (#3152)

* add eslint to src project

* fix test

---------

Co-authored-by: Rob Larsen <rob@htmlcssjavascript.com>

src/eslint.config.mjs

@@ -0,0 +1,9 @@
+import globals from 'globals';
+import pluginJs from '@eslint/js';
+
+export default [
+  {
+    languageOptions: { globals: globals.browser },
+  },
+  pluginJs.configs.recommended,
+];

src/package.json

@@ -11,14 +11,18 @@
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
     "start": "webpack serve --open --config webpack.config.dev.js",
-    "build": "webpack --config webpack.config.prod.js"
+    "lint": "eslint ./js --fix",
+    "build": "npm run lint && webpack --config webpack.config.prod.js"
   },
   "devDependencies": {
-    "copy-webpack-plugin": "^13.0.0",
-    "html-webpack-plugin": "^5.6.3",
-    "webpack": "^5.99.9",
-    "webpack-cli": "^6.0.1",
-    "webpack-dev-server": "^5.2.1",
-    "webpack-merge": "^6.0.1"
+    "@eslint/js": "^9.9.0",
+    "copy-webpack-plugin": "^11.0.0",
+    "eslint": "^8.57.0",
+    "globals": "^15.9.0",
+    "html-webpack-plugin": "^5.6.0",
+    "webpack": "^5.92.1",
+    "webpack-cli": "^5.1.4",
+    "webpack-dev-server": "^5.0.4",
+    "webpack-merge": "^5.10.0"
   }
 }

test/file_existence.mjs

@@ -34,6 +34,7 @@ const expectedFilesInDistDir = [
 
   'index.html',
 
+  'eslint.config.mjs',
   'js/',
   'js/app.js',
   'js/vendor/',