install and run prettier

.eslintrc

@@ -0,0 +1,16 @@
+{
+  "parserOptions": {
+    "ecmaVersion": 2019,
+    "sourceType": "module",
+    "ecmaFeatures": {
+      "jsx": true
+    }
+  },
+  "extends": ["eslint:recommended"],
+  "rules": {
+    "strict": ["error", "never"]
+  },
+  "env": {
+    "browser": true
+  }
+}

package.json

@@ -4,11 +4,15 @@
   "author": "Kent C. Dodds (http://kentcdodds.com/)",
   "license": "GPLv3",
   "scripts": {
-    "build": "babel src --out-dir dist"
+    "build": "babel src --out-dir dist",
+    "lint": "eslint --ignore-path .gitignore .",
+    "format": "prettier --ignore-path .gitignore --write \"**/*.+(js|json)\""
   },
   "devDependencies": {
     "@babel/cli": "^7.7.0",
     "@babel/core": "^7.7.2",
-    "@babel/preset-env": "^7.7.1"
+    "@babel/preset-env": "^7.7.1",
+    "eslint": "^6.6.0",
+    "prettier": "^1.19.1"
   }
 }

src/example.js

@@ -1,12 +1,10 @@
-'use strict'
+const username = "freddy";
+typeof username === "string";
 
-const username = 'freddy'
+if (!("serviceWorker" in navigator)) {
-typeof username === 'strng'
-
-if (!'serviceWorker' in navigator) {
   // you have an old browser :-(
 }
 
-const greeting = 'hello'
+const greeting = "hello";
-console.log('${greeting} world!')
+console.log(`${greeting} world!`);
-[1, 2, 3].forEach(x => console.log(x))
+[1, 2, 3].forEach(x => console.log(x));