tsconfig.json

{
  "compilerOptions": {
    "allowUnreachableCode": false,
    "declaration": true,
    "esModuleInterop": true,
    "lib": [
      "dom",
      "es2015"
    ],
    "module": "es2015",
    "moduleResolution": "node",
    "noFallthroughCasesInSwitch": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "outDir": "dist/esm",
    "pretty": true,
    "sourceMap": true,
    "strict": true,
    "target": "es2015"
  },
  "files": [
    "src/index.ts"
  ]
}