javascript - Why isn't Error's stack property included in Object.keys?

Question

env: nodejs 8.1.5, also tested on jscomplete with same results

const error = new Error("message");
const { message, ...rest } = error;
const keys = Object.keys(error);
const hasStack = error.hasOwnProperty("stack");

The rest object turns out to not include the stack property because Object.keys does not return it and a "for in" will not pick it up. It is, however, an own property of the error object (hasStack is true above).

What gives? I couldn't find anything about special-casing this property in the documentation or the polyfill on https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys

Answer 1

It's not enumerable, so it won't be included in Object.keys or a for..in iteration:

const error = new Error("message");
// For Chrome, it's directly on the object:
console.log(Object.getOwnPropertyDescriptor(error, 'stack'));
// For Firefox, it's a getter on the prototype:
console.log(Object.getOwnPropertyDescriptor(Object.getPrototypeOf(error), 'stack'));