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'. */,
    "lib": [
      "es2017",
      "dom"
    ] /* Specify library files to be included in the compilation. */,
    "sourceMap": true /* Generates corresponding '.map' file. */,
    "outDir": ".build" /* Redirect output structure to the directory. */,
    "rootDir": "./" /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */,
    /* Strict Type-Checking Options */
    "strict": true /* Enable all strict type-checking options. */,
    "strictNullChecks": true /* Enable strict null checks. */,
    "alwaysStrict": true /* Parse in strict mode and emit "use strict" for each source file. */,
    /* Module Resolution Options */
    "esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "resolveJsonModule": true
  }
}