tsconfig.json

{
  "compilerOptions": {
    "pretty" : true,
    "target": "es5",           /* 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": ["es5"],            /* Specify library files to be included in the compilation. */
    "declaration": true,       /* Generates corresponding '.d.ts' file. */
    "declarationMap": true,    /* Generates a sourcemap for each corresponding '.d.ts' file. */
    "sourceMap": true,         /* Generates corresponding '.map' file. */
    "outDir": "./lib",         /* Redirect output structure to the directory. */
    "rootDirs": ["./src"],           /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    "strict": true,            /* Enable all strict type-checking options. */
    "allowSyntheticDefaultImports": true    /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
  },
  "exclude": ["./test", "**/*.d.ts", "./lib", "node_modules"]
}