prettier --list-different

.eslintrc

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

.prettierrc

@@ -0,0 +1,17 @@
+{
+  "arrowParens": "avoid",
+  "bracketSpacing": false,
+  "htmlWhitespaceSensitivity": "css",
+  "insertPragma": false,
+  "jsxBracketSameLine": false,
+  "jsxSingleQuote": false,
+  "printWidth": 80,
+  "proseWrap": "always",
+  "quoteProps": "as-needed",
+  "requirePragma": false,
+  "semi": false,
+  "singleQuote": true,
+  "tabWidth": 2,
+  "trailingComma": "all",
+  "useTabs": false
+}

package.json

@@ -4,11 +4,19 @@
   "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 .",
+    "prettier": "prettier --ignore-path .gitignore \"**/*.+(js|json)\"",
+    "format": "npm run prettier -- --write",
+    "check-format": "npm run prettier -- --list-different",
+    "validate": "npm run check-format && npm run lint && npm run build"
   },
   "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",
+    "eslint-config-prettier": "^6.5.0",
+    "prettier": "^1.19.1"
   }
 }

src/example.js

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