6.x querystring.parse returns object for which instanceof Object is false (was true for 4.x)

[kosmjon]

• Version: 6.3.1 and also 6.6.0
• Platform: Windows 7 x64 and also Centos 64 x86
  Linux ip-10-0-0-35.localdomain 3.10.0-229.14.1.el7.x86_64 deps: update openssl to 1.0.1j #1 SMP Tue Sep 15 15:05:51 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem: querystring

Here is a snippet that demos the problem:

var params, qs = require('querystring');
params = qs.parse('languageId=en-US');
console.log('%j %s', params, typeof params);
if (params instanceof Object) {
  console.log('params instanceof Object is true');
} else {
  console.log('params instanceof Object is false');
}

On 4.4.4 prints:
{"languageId":"en-US"} object
params instanceof Object is true
On 6.3.1 and 6.6.0 prints:
{"languageId":"en-US"} object
params instanceof Object is false

[targos]

This was an intended change. The object returned by querystring.parse inherits from null instead of Object since v6.0.0.

See #6055 and https://github.com/nodejs/node/wiki/Breaking-changes-between-v5-and-v6#querystring

[imyller]

Basicly this happens because typeof Object.create(null) is object, but Object.create(null) instanceof Object evaluates to false.

[claudiorodriguez]

You should check for params !== null && typeof params === 'object' (typeof null is 'object')

[imyller]

So, Object.create(null) does not inherit any properties of Object and thus is not instanceof Object.

querystring.parse() now returns this kind of "object".

As @claudiorodriguez pointed out you should use typeof

[kosmjon]

The affected code is in a 3rd-party module which I guess we will have to pull into our project to fix. This seems like a very silly code-breakage that would have been an easy fix in querystring.parse to make it behave as before. Thanks for the information.

[bnoordhuis]

This seems like a very silly code-breakage that would have been an easy fix in querystring.parse to make it behave as before.

Something tells me you didn't actually read through #6055.

[kosmjon]

You are correct. Sorry about that. I get it now. Thanks to everyone that commented and helped me to understand.

[bnoordhuis]

No problem, glad it got cleared up.