How to check for array containing only an empty object [{}]

Question

I have a variable which is as follows.

let response = [
 {}
];

Which is an array with an empty object. What kind of check should I put in place to determine if this response is exactly equal to this. i.e,

[{}] === response; // returns false

I want to have a check that returns false if the response is [{}] how do i do that.

There are already questions on stack-overflow which asks on how to check for an empty object. My Question is that how do I check for an array with an empty object. So completely different. This is no duplicate of any question.

I would try something like that: Array.isArray(response) && response.length === 1 && typeof response[1] === 'object' && Object.keys(response[1]).length === 0 — dhilt
– dhilt, Commented Dec 20, 2017 at 15:00
@FelixKling this is not a duplicate of that question. As this question ask an empty object inside an array. That question asks only for an empty object. :) — Adeel Imran
– Adeel Imran, Commented Dec 20, 2017 at 15:01
@AdeelImran: I would expect that you know how to check the length of the array and how to access the first element :) "So completely different." Not quite. Checking the emptiness of an object is a part of your problem. — Felix Kling
– Felix Kling, Commented Dec 20, 2017 at 15:03
arr.length === 1 && isEmptyObject(arr[0]) where isEmptyObject is an implementation suggested in the other question. — Felix Kling
– Felix Kling, Commented Dec 20, 2017 at 15:07

Luan Nico · Accepted Answer · 2017-12-20 14:58:51Z

1

First check if it is an array, with Array.isArray, then check the .length to see if it's one, then check if the first element is an empty object (typeof and Object.keys().length === 0). That way you'll be pretty sure it's what you wanted.

Another option is to use json: JSON.stringify(response) ==== '[{}]'. Just beware of cyclic dependencies in response.

answered Dec 20, 2017 at 14:58

Luan Nico

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2 Comments

Adeel Imran Over a year ago

Thank you sir. This helped.

Ayush Gupta Over a year ago

just an FYI, typeof [] is object, and Object.keys([]).length is 0, so you might want to do a different check for object

Ayush Gupta · Accepted Answer · 2017-12-20 14:59:35Z

1

You can simply do:

let response = [{}];

console.log(JSON.stringify([{}]) === JSON.stringify([{}])); // true,

But if your response is cyclic, this will fail.

Another way you can do is:

let response = [{}];


console.log(
  Array.isArray(response) &&
    response.length === 1 &&
    Object.prototype.toString.call(response[0]) === '[object Object]' &&
    Object.getOwnPropertyNames(response[0]).length === 0
); // true

answered Dec 20, 2017 at 14:59

Ayush Gupta

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1 Comment

Luan Nico Over a year ago

For the cyclic problem, I believe there is an option for stringify that will go just n-levels deep, fixing the problem (if the structure is cyclic, it certainly going to be different 2-level deep anyway). I'd need to look it up, though

Ivan Velichko · Accepted Answer · 2017-12-20 15:00:17Z

0

How about:

Object.keys(response[0] || {}).length === 0

answered Dec 20, 2017 at 15:00

Ivan Velichko

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4 Comments

Luan Nico Over a year ago

It could be an array with more than one element, but might work for most use-cases ;)

Ayush Gupta Over a year ago

Wont work in case of [[]] as Object.keys([]).length is 0

erikvimz Over a year ago

@AyushGupta But that's not what the OP is asking for.

Ayush Gupta Over a year ago

Perhaps, but if the OP needs to check for that response exactly, and [[]] is a valid response , yours wont be 100% reliable

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