Check if array is empty or null

Question

I would like to know how to check if an array is empty or null in jQuery. I tried array.length === 0 but it didn't work. It did not throw any error either.

This is the code:

var album_text = new Array();

$("input[name='album_text[]']").each(function(){
  if( $(this).val() &&  $(this).val() != '') {
    album_text.push($(this).val());
  }
});
if (album_text.length === 0) {
  $('#error_message').html("Error");
}

else {
  // send data
}

Roselleroselyn

The same way as in "normal JavaScript": #2672880 – Mccants

@Julien, I tried all of those solutions listed in that thread before starting this thread. None of them worked somehow. – Roselleroselyn

Can we get some more code for context? Surrounding JavaScript, HTML? Are you sure that $("input[name='album_text[]']") is actually returning elements? – Obmutescence

@JulienSchmidt: the question you linked to is about checking if an array value is empty, not the entire array. – Sergius

Answer 1

As long as your selector is actually working, I see nothing wrong with your code that checks the length of the array. That should do what you want. There are a lot of ways to clean up your code to be simpler and more readable. Here's a cleaned up version with notes about what I cleaned up.

var album_text = [];

$("input[name='album_text[]']").each(function() {
    var value = $(this).val();
    if (value) {
        album_text.push(value);
    }
});
if (album_text.length === 0) {
    $('#error_message').html("Error");
}

else {
  //send data
}

Some notes on what you were doing and what I changed.

1. $(this) is always a valid jQuery object so there's no reason to ever check if ($(this)). It may not have any DOM objects inside it, but you can check that with $(this).length if you need to, but that is not necessary here because the .each() loop wouldn't run if there were no items so $(this) inside your .each() loop will always be something.
2. It's inefficient to use $(this) multiple times in the same function. Much better to get it once into a local variable and then use it from that local variable.
3. It's recommended to initialize arrays with [] rather than new Array().
4. if (value) when value is expected to be a string will both protect from value == null, value == undefined and value == "" so you don't have to do if (value && (value != "")). You can just do: if (value) to check for all three empty conditions.
5. if (album_text.length === 0) will tell you if the array is empty as long as it is a valid, initialized array (which it is here).

What are you trying to do with this selector $("input[name='album_text[]']")?

Silurid

@MaciekSemik - see #359994. I always use strict equality (===) unless I specifically want to allow a type conversion. It's a good habit to get into. – Silurid

Answer 2

User JQuery is EmptyObject to check whether array is contains elements or not.

var testArray=[1,2,3,4,5];
var testArray1=[];
console.log(jQuery.isEmptyObject(testArray)); //false
console.log(jQuery.isEmptyObject(testArray1)); //true

Deviant

Much more reliable than checking the length, especially if your variable can also be an object (with objects, length do not work to check if empty). – Giaour

This is the more appropriate answer in my opinion. – Clew

isEmptyObject always returns false if Array.prototype is extended, e.g. Array.prototype.someFunction = function () {}; - even if the array is empty. Note that some frameworks (e.g. Ember.js) extend Array prototype by default. – Isle

Be careful with isEmptyObject!For jQuery 1.8.3 jQuery.isEmptyObject([]) returns false, but for jQuery 1.11.3 it returns true. Actually, jQuery documentation says The argument should always be a plain JavaScript Object as other types of object (DOM elements, primitive strings/numbers, host objects) may not give consistent results across browsers. Sorry, didn't see @rhinoxi 's answer. – Thoracoplasty

Answer 3

I think it is dangerous to use $.isEmptyObject from jquery to check whether the array is empty, as @jesenko mentioned. I just met that problem.

In the isEmptyObject doc, it mentions:

The argument should always be a plain JavaScript Object

which you can determine by $.isPlainObject. The return of $.isPlainObject([]) is false.

Inkerman

Answer 4

You should check for '' (empty string) before pushing into your array. Your array has elements that are empty strings. Then your album_text.length === 0 will work just fine.

Unshackle

Please see the updated the code. I added this code if( $(this).val() && $(this).val() != '') yet it does not work. – Roselleroselyn

Answer 5

/*
  Basic Checking with undefined array for Jquery Array
*/
if (typeof myArray !== 'undefined' && myArray.length > 0) {
    console.log('myArray is not empty.');
}else{
    console.log('myArray is empty.');
}

Mcbrayer