index.js // Extending JavaScript with ease (beginner level tutorial)

index.ts

// The only significant difference between TS and JavaScript is interface.
// Interface declarates that object passed as `obj` should be an object actually
interface PassedObject {
  readonly [key: string]: any;
}

// Same logic as in our ES6 code
const objectFetch = (obj: PassedObject, property: string): any => {
  // tslint:disable-next-line:no-if-statement
  if (obj.hasOwnProperty(property)) {
    return obj[property];
  }

  throw new ReferenceError(`No such property: ${property}`);
};

export default objectFetch;