{
  "compilerOptions": {
    "target": "es2017",
    "outDir": "./",
    "declaration": true,
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "removeComments": false,
    "noUnusedLocals": true,
    "typeRoots": [
      "./node_modules/@types"
    ],
    "lib": ["dom", "es5", "es2015", "scripthost"]
  },
  "formatCodeOptions": {
    "indentSize": 2,
    "tabSize": 2
  },
  "files": [
    "src/core/index.ts"
  ],
  "include": [
    "src/**/*.ts",
    "src/**/*.spec.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

{
  "compilerOptions": {
    "target": "es2016",
    "outDir": "./",
    "declaration": true,
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "removeComments": false,
    "noUnusedLocals": true,
    "typeRoots": [
      "./node_modules/@types"
    ],
    "lib": ["dom", "es5", "es2015", "scripthost"]
  },
  "formatCodeOptions": {
    "indentSize": 2,
    "tabSize": 2
  },
  "files": [
    "src/core/index.ts"
  ],
  "include": [
    "src/**/*.ts",
    "src/**/*.spec.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

Change compile target to es6
Change compile target to es6
