JavaScript How to define an array of undefined length of empty objects? - Stack Overflow

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var array = [];

var object = {};

Now, I need an array of empty objects.

array[0] = {};
array[1] = {};
//........
//........

and

var array = [{}];

is obviously not right.

How to define array of (empty) objects in JS?

var array = [{},{},{},{},.........];

Thanks.

EDIT:

The reason I need is the same reason that having an array with undefined length is useful, and mathematically natural in some cases.

I need object wrappers, and for initialization, it's just an empty object, like some values are null or undefined in many cases.

so, I'll have

var object = {};

array[0].value = 'foo', array[1].value = 'bar'.....

However, I do need multiple object wrappers, and the number is not pre-determined, so consequently, I need an arrays of the objects.

So, I am sorry, I modify my Question title

JavaScript How to define an array of undefined length of empty objects?

var array = [];

var object = {};

Now, I need an array of empty objects.

array[0] = {};
array[1] = {};
//........
//........

and

var array = [{}];

is obviously not right.

How to define array of (empty) objects in JS?

var array = [{},{},{},{},.........];

Thanks.

EDIT:

The reason I need is the same reason that having an array with undefined length is useful, and mathematically natural in some cases.

I need object wrappers, and for initialization, it's just an empty object, like some values are null or undefined in many cases.

so, I'll have

var object = {};

array[0].value = 'foo', array[1].value = 'bar'.....

However, I do need multiple object wrappers, and the number is not pre-determined, so consequently, I need an arrays of the objects.

So, I am sorry, I modify my Question title

JavaScript How to define an array of undefined length of empty objects?

• javascript

Share Improve this question Follow edited Feb 3, 2014 at 7:36 asked Feb 2, 2014 at 4:52 user1028880user1028880 7

• 2 you just need to declare an empty array and push an object int o it like array.push(object).. – Deepak Ingole Commented Feb 2, 2014 at 4:53
• 2 whats wrong with var array = [{}]; that will give you an array containing one empty object? – ericjbasti Commented Feb 2, 2014 at 4:56
• There is no problem writing var array = [{}, {}, {}]; to make an array of objects. – Jonn Commented Feb 2, 2014 at 4:58
• why would you need that? I'm curious about the engineering protocole behind that – Sebas Commented Feb 2, 2014 at 5:00
• Sebas, good quesion, I edit my Q. – user1028880 Commented Feb 2, 2014 at 5:04

 |  Show 2 more ments

4 Answers 4

Sorted by: Reset to default 3

Arrays can grow and shrink dynamically. So from a certain point of view, they are already of undefined length. You can always add new objects to it if you want to.

You can also create a helper function which checks first if an object exists at a certain position and if not, creates a new one.

You mentioned array[2].value = 'foo' as an example. Here is a helper function that you could use:

function getObjectAtIndex(arr, index) {
    return arr[index] || (arr[index] = {});
}

and then, instead of writing array[2].value = 'foo', you'd write:

getObjectAtIndex(array, 2).value = 'foo'

In your array, pushing object in any way is right. That's totally ok. like:

var arr = [];
arr.push({}); // ok
aa[1] = {} // also ok

or:

var arr = [{}, {}, {}]; // the way you are doing is also fine

Or, if you want to do it via loop, that is also fine. Like:

var arr = [];
for(var i=0; i<5; i++){
    arr[i] = {};
}

In general, the way to write

var array = [];
array[0] = {};
array[1] = {};
//........
//........

in a sane manner without lots of copy paste is to use a for loop:

var array = [];
for(var i=0; i<10; i++){
  array[i] = {};
}

I'm pretty sure that an array like var array = []; is an array of Objects. Based on how Javascript works, you never have to worry about null-pointer exceptions, so just define the array and act like you initialized it with the empty objects and see if it works

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