{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es2015",
    "noImplicitAny": true,
    "sourceMap": true,
    "declaration": true,
    "outDir": "dist/"
  },
  "files": [
    "src/index.ts"
  ]
}

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es2017",
    "noImplicitAny": true,
    "sourceMap": true,
    "declaration": true,
    "outDir": "dist/"
  },
  "files": [
    "src/index.ts"
  ]
}

Upgrade compile target to es2017
Upgrade compile target to es2017
