add npm-run-all --parallel

.eslintrc

@@ -1,18 +1,23 @@
 {
+  "parser": "@typescript-eslint/parser",
   "parserOptions": {
     "ecmaVersion": 2019,
     "sourceType": "module",
     "ecmaFeatures": {
       "jsx": true
-    }
     },
+    "project": "./tsconfig.json"
+  },
+  "plugins": ["@typescript-eslint/eslint-plugin"],
+  "extends": [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/eslint-recommended",
+    "plugin:@typescript-eslint/recommended",
+    "eslint-config-prettier",
+    "eslint-config-prettier/@typescript-eslint"
+  ],
   "rules": {
-    "strict": ["error", "never"],
-    "valid-typeof": "error",
-    "no-unsafe-negation": "error",
-    "no-unused-vars": "error",
-    "no-unexpected-multiline": "error",
-    "no-undef": "error"
+    "strict": ["error", "never"]
   },
   "env": {
     "browser": true

.huskyrc

@@ -0,0 +1,5 @@
+{
+  "hooks": {
+    "pre-commit": "npm run check-types && lint-staged"
+  }
+}

.lintstagedrc

@@ -0,0 +1,9 @@
+{
+  "*.js": [
+    "eslint"
+  ],
+  "*.+(js|json|ts)": [
+    "prettier --write",
+    "git add"
+  ]
+}

.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

@@ -4,12 +4,26 @@
   "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 --ext .js,.ts,.tsx .",
+    "check-types": "tsc",
+    "prettier": "prettier --ignore-path .gitignore --write \"**/*.+(js|json)\"",
+    "format": "npm run prettier -- --write",
+    "check-format": "npm run prettier -- --list-different",
+    "validate": "npm-run-all --parallel check-types check-format lint build"
   },
   "devDependencies": {
-    "@babel/cli": "^7.7.0",
-    "@babel/core": "^7.7.2",
-    "@babel/preset-env": "^7.7.1",
-    "eslint": "^6.6.0"
+    "@babel/cli": "^7.5.5",
+    "@babel/core": "^7.5.5",
+    "@babel/preset-env": "^7.5.5",
+    "@typescript-eslint/eslint-plugin": "^2.0.0",
+    "@typescript-eslint/parser": "^2.0.0",
+    "eslint": "^6.1.0",
+    "eslint-config-prettier": "^6.0.0",
+    "husky": "^3.0.2",
+    "lint-staged": "^9.2.1",
+    "npm-run-all": "^4.1.5",
+    "prettier": "^1.18.2",
+    "typescript": "^3.5.3"
   }
 }

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))

src/typescript-example.ts

@@ -0,0 +1,21 @@
+function add(a: number, b: number): number {
+  return a + b
+}
+
+interface User {
+  name: {
+    first: string
+    middle: string
+    last: string
+  }
+}
+function getFullName(user: User): string {
+  const {
+    name: {first, middle, last},
+  } = user
+  return [first, middle, last].filter(Boolean).join('')
+}
+
+add(1, 2)
+
+getFullName({name: {first: 'Joe', middle: 'Bud', last: 'Matthews'}})

tsconfig.json

@@ -0,0 +1,9 @@
+{
+  "compilerOptions": {
+    // because we're compiling with Babel instead of TypeScript
+    // and we're only using TypeScript for type checking, we'll set "noEmit"
+    // to true so running type checking doesn't generate any files.
+    "noEmit": true,
+    "baseUrl": "./src"
+  }
+}