Today, during some testing, I was interested in seeing all properties of an Error object.

I wrote this Method to get all available properties, not caring about ‘hasOwnProperty’.

/**
 * Get all properties of an object and don't care about enumerable or prototyp.
 *
 * @internal
 * @param {object} obj
 * @return {[string, unknown][]}
 */
export function getAllProperties(obj: object): [string, unknown][] {
  const properties: [string, unknown][] = [];
  const prototypChain: string[] = [];
  let currentObj = obj;

  while (currentObj !== Object.prototype && currentObj !== null) {
    Object.getOwnPropertyNames(currentObj).forEach((key) => {
      if (prototypChain.length > 0) {
        // @ts-expect-error I want it this way!
        properties.push([`${prototypChain.join('.')}.${key}`, currentObj[key]]);
      } else {
        // @ts-expect-error I want it this way!
        properties.push([key, currentObj[key]]);
      }
    });
    currentObj = Object.getPrototypeOf(currentObj);
    prototypChain.push('prototyp');
  }
  return properties;
}

Imagine my surprise when I used it to look at an error thrown with new Error('...').

{
  stack: "Error: This is a test error
    at Object.<anonymous> (/Users/.../Entwicklung/Bit/bit-log/src/appender/__tests__/FileAppender.spec.ts:256:13)",
  message: "This is a test error",
  prototyp.constructor: [Function function Error() { [native code] }],
  prototyp.name: "Error",
  prototyp.message: "",
  prototyp.toString: [Function function toString() { [native code] }]
}

How is it possible to have an object with inheritance that does not correctly overwrite a property in the parent?
Or is my expectation wrong that there should not be two different message properties?

After all, this is a standard object and not a custom implementation.