tsconfig.json

{
    "compilerOptions": {
        "target": "es5",
        "module": "commonjs",
        "declaration": true,
        "sourceMap": true,
        "importHelpers": true,
        "experimentalDecorators": true,
        "removeComments": true,
        "lib": [
            "es2015"
        ],
        "outDir": "./dist",
        "rootDir": "./src",
        "downlevelIteration": true
    }
}