tsconfig.json

{
  "compilerOptions": {
    /* Basic Options */
    "target": "es2015",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
    "lib": ["es2015"],
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    "sourceMap": true,                     /* Generates corresponding '.map' file. */
    "outFile": "./dist/build.js",                       /* Concatenate and emit output to single 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. */
    "noImplicitAny": false,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    "strictNullChecks": true,              /* Enable strict null checks. */
    "strictFunctionTypes": true,           /* Enable strict checking of function types. */
    "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
    "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */

    /* Module Resolution Options */
    // "types": [],                           /* Type declaration files to be included in compilation. */
    "esModuleInterop": true,               /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */

    /* Experimental Options */
     "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
     "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
  }
}