tsconfig.json

{
  "compilerOptions": {
    "target": "es2015",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
    "rootDirs": [ "./src", "./tests" ],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    "incremental": true,                   /* Enable incremental compilation */
    "declaration": true,
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
    "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    "esModuleInterop": true,                   /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
    "sourceMap": true,                     /* Generates corresponding '.map' file. */
    "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
    "outDir": "./out",                        /* Redirect output structure to the directory. */
    "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    "strict": true,                           /* Enable all strict type-checking options. */
    "assumeChangesOnlyAffectDirectDependencies": true
  }
}