Convert to TypeScript (wojtekmaj#14)

.babelrc

@@ -1,8 +1,3 @@
 {
-  "presets": ["@babel/env"],
-  "env": {
-    "production-esm": {
-      "presets": [["@babel/env", { "modules": false }]]
-    }
-  }
+  "presets": ["@babel/typescript", "@babel/env"]
 }

.eslintrc.json

@@ -1,3 +1,9 @@
 {
-  "extends": "wojtekmaj"
+  "extends": [
+    "wojtekmaj",
+    "plugin:@typescript-eslint/eslint-recommended",
+    "plugin:@typescript-eslint/recommended"
+  ],
+  "parser": "@typescript-eslint/parser",
+  "plugins": ["@typescript-eslint"]
 }

package.json

@@ -4,19 +4,21 @@
   "description": "A function that returns a flag emoji given IETF language tag.",
   "main": "dist/cjs/index.js",
   "module": "dist/esm/index.js",
-  "source": "src/index.js",
+  "source": "src/index.ts",
+  "types": "src/index.ts",
   "sideEffects": false,
   "scripts": {
     "build": "yarn build-esm && yarn build-cjs",
-    "build-esm": "BABEL_ENV=production-esm babel src -d dist/esm --ignore \"**/*.spec.js\"",
-    "build-cjs": "BABEL_ENV=production-cjs babel src -d dist/cjs --ignore \"**/*.spec.js\"",
+    "build-esm": "tsc --project tsconfig.build.json --outDir dist/esm --module esnext",
+    "build-cjs": "tsc --project tsconfig.build.json --outDir dist/cjs --module commonjs",
     "clean": "rimraf dist",
     "jest": "jest",
-    "lint": "eslint src",
+    "lint": "eslint src --ext .js,.ts",
     "postinstall": "husky install",
     "prepack": "yarn clean && yarn build",
     "prettier": "prettier --check . --cache",
-    "test": "yarn lint && yarn prettier && yarn jest"
+    "test": "yarn lint && yarn tsc && yarn prettier && yarn jest",
+    "tsc": "tsc --noEmit"
   },
   "keywords": [
     "emoji"
@@ -27,16 +29,20 @@
   },
   "license": "MIT",
   "devDependencies": {
-    "@babel/cli": "^7.15.0",
     "@babel/core": "^7.15.0",
     "@babel/preset-env": "^7.15.0",
+    "@babel/preset-typescript": "^7.18.6",
+    "@types/jest": "^29.0.0",
+    "@typescript-eslint/eslint-plugin": "^5.41.0",
+    "@typescript-eslint/parser": "^5.44.0",
     "eslint": "^8.26.0",
     "eslint-config-wojtekmaj": "^0.7.1",
     "husky": "^8.0.0",
     "jest": "^29.0.0",
     "prettier": "^2.7.0",
     "pretty-quick": "^3.1.0",
-    "rimraf": "^3.0.0"
+    "rimraf": "^3.0.0",
+    "typescript": "^4.9.4"
   },
   "resolutions": {
     "semver@7.0.0": "^7.0.0"

src/index.spec.js → src/index.spec.ts

@@ -2,9 +2,10 @@ import countryCodeToFlagEmoji from './index';
 
 describe('countryCodeToFlagEmoji', () => {
   it('returns nothing given nothing', () => {
+    // @ts-expect-error-next-line
     const result = countryCodeToFlagEmoji();
 
-    expect(result).toBe();
+    expect(result).toBe(null);
   });
 
   it('returns proper emoji from a full IETF language tag', () => {

src/index.ts

@@ -0,0 +1,20 @@
+// Translates 'a' to '🇦', 'b' to '🇧' and so on.
+function letterToLetterEmoji(letter: string): string {
+  return String.fromCodePoint(letter.toLowerCase().charCodeAt(0) + 127365);
+}
+
+// Translates 'pl' to 'PL', 'en-US' to 'US' and so on.
+function countryCodeToCountry(countryCode: string): string {
+  const country = countryCode.split('-').pop() as string;
+
+  return country.toUpperCase();
+}
+
+// Translates 'pl-PL' to 🇵🇱 and so on.
+export default function countryCodeToFlagEmoji(string: string): string | null {
+  if (!string) {
+    return null;
+  }
+
+  return Array.from(countryCodeToCountry(string)).map(letterToLetterEmoji).join('');
+}

tsconfig.build.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./tsconfig.json",
+  "exclude": ["src/**/*.spec.ts"]
+}

tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "declaration": true,
+    "esModuleInterop": true,
+    "isolatedModules": true,
+    "moduleResolution": "node",
+    "outDir": "dist",
+    "strict": true
+  },
+  "include": ["src"]
+}