tsconfig.json

{
  "compilerOptions": {
    /* Basic Options */
    "target": "es2017",                       /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
    "declaration": true,                      /* Generates corresponding '.d.ts' file. */
    "outDir": "./built/",                     /* Redirect output structure to the directory. */
    "rootDir": "./src/",                      /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    "removeComments": true,                   /* Do not emit comments to output. */

    /* Strict Type-Checking Options */
    "strict": true,                           /* Enable all strict type-checking options. */
    "strictFunctionTypes": true,              /* Enable strict checking of function types. */

    /* Additional Checks */
    "noImplicitReturns": true,                /* Report error when not all code paths in function return a value. */

    /* Module Resolution Options */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
  },
  "include": [
    "src/**/*",
  ],
  "exclude": [
      "node_modules",
      "test/**/*",
  ]
}