eslint extends

.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

@@ -9,6 +9,7 @@
   "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"
   }
 }

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('${greeting} world!')
+console.log(`${greeting} world!`)
-[1, 2, 3].forEach(x => console.log(x))
+;[1, 2, 3].forEach(x => console.log(x))