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.         


        

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'));

To iterate over all properties, including non-enumerable ones, use Object.getOwnPropertyNames instead:

// Chrome:
const error = new Error("message");
Object.getOwnPropertyNames(error).forEach((propName) => {
  console.log(propName);
});

On Firefox, those two properties are getters on the prototype, rather than being directly on the error object. (The prototype also has other properties other than stack and message)

// Chrome:
const error = new Error("message");
Object.getOwnPropertyNames(Object.getPrototypeOf(error)).forEach((propName) => {
  console.log(propName);
});