class CustomError extends Error {
    constructor(message: string) {
      super(`Lorem "${message}" ipsum dolor.`);
      this.name = 'CustomError';
    }
}
throw new CustomError('foo');

class FooError extends Error {
    constructor(m: string) {
        super(m);

        // Set the prototype explicitly.
        Object.setPrototypeOf(this, FooError.prototype);
    }

    sayHello() {
        return "hello " + this.message;
    }
}

class CustomError extends Error {
  constructor(message?: string) {
    // 'Error' breaks prototype chain here
    super(message);
    // restore prototype chain
    // (alternatively use Object.setPrototypeOf if you have an ES6 environment.)
    this.__proto__ = new.target.prototype;

  }
}