Making custom error type in Javascript

custom_error.js

// Making custom error types
// Taken from the comment at https://blog.getify.com/howto-custom-error-types-in-javascript/
//
function makeErrorType() {
  var it = function (message) {
    if (!(this instanceof it)) {
      return new it(message);
    }
    this.message = message;
    this.stack = new Error(message).stack;
  }
  it.prototype = Object.create(Error.prototype);
  return it;
}

////////////////////////////
// in action:

let MyError = makeErrorType();
let MyError2 = makeErrorType();

try {
  throw new MyError("some message");
} catch (err) {
  console.log(err.message);               // some message
  console.log(err instanceof MyError);    // true
  console.log(err instanceof MyError2);   // false
  console.log(err instanceof Error);      // true
}