tsconfig.json

{
  "compilerOptions": {
    // Target latest version of ECMAScript.
    "target": "ES5",
    // Search under node_modules for non-relative imports.
    "moduleResolution": "node",
    // Process & infer types from .js files.
    //    "allowJs": true,
    "declaration": true,
    "outDir": "lib",                          /* Redirect output structure to the directory. */
    "rootDir": "src",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // Enable strictest settings like strictNullChecks & noImplicitAny.
    "strict": true,
    // Disallow features that require cross-file information for emit.
    "isolatedModules": false,
    // Import non-ES modules as default imports.
    "esModuleInterop": true,
    "allowSyntheticDefaultImports": true,
    "lib": ["esnext"],
    "types": [
      "node",
      "jest"
    ],
    "module": "commonjs"
  },
  "include": ["src/**/*.ts"],
  "exclude": ["src/**/*.test.ts"]
}