How to check emptiness with single condition regardless of input is object or array in Javascript

Question

I am writing a conditional statement which execute if an input is not empty but the issue is that input can either object or array.

if(response && response.length > 0 ) {
 // but this failed if response is an object
}

So I am looking for single condition which check for both (object and array) in one line. Moreover, I checked that typeof of array and object are object

        var object_ = {};
        var array_ = [];
        console.log('typeof object', typeof object_); // object
        console.log('typeof array', typeof array_); // object

Possible duplicate of https://stackoverflow.com/questions/679915/how-do-i-test-for-an-empty-javascript-object — abhishekkannojia, Aug 11 '17 at 12:31
not duplicate; I am seeking for a single method of object and array checking — diEcho, Aug 11 '17 at 12:33
Given Array is also an Object, you can simply use: if (response && response instanceof Object) — tibetty, Aug 11 '17 at 12:34
@XihuaDuan No, the question if, how can he check if an object is empty when it's both array or object in one condition — Icepickle, Aug 11 '17 at 12:48
I see, but answer#2 has a flaw as well, please read my new post. — tibetty, Aug 11 '17 at 15:01

Jonas Wilms · Answer 1 · 2017-08-11T12:40:35.983

4

if(Object.keys(response).length)

Simply check if there are keys in the object.

Note that Object.keys will return the following:

{} => []
{a:undefined} => ["a"]
[] => []
["a"] => [0]
"a" => [0] //strings are arraylike
undefined => Error

edited Aug 11 '17 at 12:40

answered Aug 11 '17 at 12:31

Jonas Wilms

106,571
13
98
120

but what if array comes as input? – diEcho Aug 11 '17 at 12:32
@pro.mean `Object.keys()` works on arrays. Why wouldn't it? – Pointy Aug 11 '17 at 12:33
I do not agree this answer. Check my answer , you need to compare the key length with greater than 0. – Ankit Agarwal Aug 11 '17 at 12:35
@AKA no you don't. – Pointy Aug 11 '17 at 12:35
@aka so then i downvote yours too because i *think* its wrong ? ( hint : it isnt) – Jonas Wilms Aug 11 '17 at 12:36
Did you check the code snippet @Jonasw which i added – Ankit Agarwal Aug 11 '17 at 12:39
1

@AKA Your edit nor your snippet changes anything to your statements here – Icepickle Aug 11 '17 at 12:40
Check properly. My answer and the snippet works as expected. I do not think it is something to be down voted. – Ankit Agarwal Aug 11 '17 at 12:42
@aka train station – Jonas Wilms Aug 11 '17 at 12:42
@Jonasw What you mean? – Ankit Agarwal Aug 11 '17 at 12:43
@Jonasw gives error when i have var response; Object.keys(a).length But mine do not – Ankit Agarwal Aug 11 '17 at 12:45
Thank you for useful demonstration as well – diEcho Aug 11 '17 at 12:45
You see that when response is undefined there is no condition that checks undefined in his answer. It simply checks the Object.keys(undefined).length. So you people say this is correct. Wow suprising – Ankit Agarwal Aug 11 '17 at 12:46
That is understandable @AKA – diEcho Aug 11 '17 at 12:48
because he also demonstrate with various scenario including undefined and string input – diEcho Aug 11 '17 at 12:49
1

Lets see, his answer was first, the OP asks for 1 condition, it gives it, OP didn't specify what the behavior should be when nothing is there, and Jonas did specify it, but most of all, he was quite relaxed in this topic, so he won the popularity vote ;) – Icepickle Aug 11 '17 at 12:50
@aka by the way, i didnt downvote your answer. And yes, the upper code fails in some cases, but if one trys to pass undefined aka nothing, the OP may wants to check that additionally, or if there always should be passed an object its quite okay to throw an error i think – Jonas Wilms Aug 11 '17 at 12:52
1

@icepickle thanks :) ( actually im not calm at all ...) – Jonas Wilms Aug 11 '17 at 12:56

Ankit Agarwal · Accepted Answer · 2017-08-11T12:41:16.027

2

Use this simple solution

if(response && Object.keys(response).length > 0) {
 //works for both object and arrays
}

Check this code snippet

       var obj1 = {};
       var obj2 = {
          'test1':'test1',
          'test2':'test2'
       };
       var arr1 = [];
       var arr2 = ['a','b','c'];

       console.log(obj1 && Object.keys(obj1).length > 0);

       console.log(obj2 && Object.keys(obj2).length > 0);

       console.log(arr1 && Object.keys(arr1).length > 0);

       console.log(arr2 && Object.keys(arr2).length > 0);

edited Aug 11 '17 at 12:41

answered Aug 11 '17 at 12:32

Ankit Agarwal

28,439
5
29
55

3

Why would you need jquery? – Icepickle Aug 11 '17 at 12:40
This is super simple. but no need of jQuery – diEcho Aug 11 '17 at 12:40
No, this answer has a flaw that it will treat a string as a valid input. – tibetty Aug 11 '17 at 14:55

score 1 · Answer 3 · answered Aug 11 '17 at 14:59

1

Answer 2 could not tell a string from Array or Object, just run this:

let s = 'hello, world';
console.log(Object.keys(s).length); // 12 will be the output

A revision should go as:

if (response instanceof Object && Object.keys(response).length > 0)

answered Aug 11 '17 at 14:59

tibetty

543
2
9

How to check emptiness with single condition regardless of input is object or array in Javascript

3 Answers3