tsconfig.json

{
  "compilerOptions": {
      "module": "commonjs",
      "moduleResolution": "node",
      "lib": ["dom", "es2015", "es2017", "es2015.iterable"],
      "jsx": "react", // uses typescript to transpile jsx to js
      "target": "es5", // specify ECMAScript target version
      "allowJs": true, // allows a partial TypeScript and JavaScript codebase
      "declaration": true,
      "checkJs": false, // checks types in .js files (https://github.com/microsoft/TypeScript/wiki/Type-Checking-JavaScript-Files)
      "allowSyntheticDefaultImports": true,
      "resolveJsonModule": true,
      "skipLibCheck": true,
      "outDir": "built",
      "downlevelIteration": true,
      "noEmit": false,
      "noImplicitAny": false,
      "esModuleInterop": true,
      "sourceMap": true
  },
  "include": [
      "index.ts",
      "./lib", // type-checks all js files as well not just .ts extension
      "@types/reproject/index.d.ts",
      "@types/@turf/distance/index.d.ts"
  ],
  "exclude": [
      "./lib/wkb",
      "built/**/*",
      "./test"
  ]
}