Node: 'constructor' bug

[mbykov]

• Version: v10.14.2
• Platform: Linux asus 4.9.133-std-def-alt0.M80P.1 #1 SMP Mon Oct 15 16:46:38 UTC 2018 x86_64 GNU/Linux
• Subsystem:

What steps will reproduce the bug?

$ node

a = {}
a['constructor']
[Function: Object]

How often does it reproduce? Is there a required condition?

What is the expected behavior?

What do you see instead?

Additional information

Sorry if it is a known bug, I could not find it. Where I can read about?

[addaleax]

@mbykov What is the expected behaviour for you here?

> a.constructor === Object
true
> Object
[Function: Object]

This seems to be right to me – a.constructor should be the built-in Object function (because a = {} is pretty much the same as a = new Object()).

[bnoordhuis]

Closing, not a bug. Please move it to nodejs/help if you have follow-up questions.

[mbykov]

a = {}
a - is empty object, right?

Object.keys(a).length
0
a['any-string'] ? true : false
false
a['constructor'] ? true : false
true

Note, I am speaking about a['sring'], not about a.string, look:

if a[key] - do smth
else - do smth else

and you will get an error when key = 'constructor' - and I have got this error already several days ago.

That is a bug, definitely. Or you must write write about this behavior explicitly. What other strings should not be used in an empty object, except 'constructor'?

[targos]

What other strings should not be used in an empty object, except 'constructor'?

All keys that exists on Object.prototype.

If you want a really "empty" object, you can create one with Object.create(null). This will set the object's prototype to null and so the object won't inherit any property.

[mbykov]

Great, thank you!