tsconfig.json

{
  "compilerOptions": {
    "target": "ES2015",
    "lib": ["es2015", "es2017.string", "dom"],
    "module": "esnext",
    "moduleResolution": "node",
    "esModuleInterop": true,
    "declaration": true,
    "outDir": "./dist/esm",
    "typeRoots": ["./node_modules/@types", "./src/typings"],
    "sourceMap": true,
    /* Strict Type-Checking Options */
    "strict": true /* Enable all strict type-checking options. */,
    "noImplicitAny": true /* 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. */,
    "strictBindCallApply": true /* Enable strict 'bind', 'call', and 'apply' methods on functions. */,
    "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. */,
    /* Additional Checks */
    "noUnusedLocals": true /* Report errors on unused locals. */,
    "noUnusedParameters": true /* Report errors on unused parameters. */,
    "noImplicitReturns": true /* Report error when not all code paths in function return a value. */,
    "noFallthroughCasesInSwitch": true /* Report errors for fallthrough cases in switch statement. */
  },
  "include": ["src/**/*.ts"]
}