Working with empty objects in javascript array

Question

I have an array of arrays that I am trying to pull values from. The problem is that I get an undefined error when it hits an empty array.

Here is the array I'm working with:

 data = [[Object { myvar=null}], [Object { myvar="testval"}], [], [], []]

Here is the javascript I'm using to get all myvar values:

myarr = [];
for (var i = 0; i < data.length; i++) {
    console.log(data[i][0].myvar);
    if (data[i][0].myvar) {
        dep = data[i][0].myvar;
        if (dep != null) {
            myarr.push(dep);
        }
    }
}

The console.log looks like:

   null
   testval
   Error: data[i][0] is undefined

So it breaks when it reaches the first []. How could I remove all the empty arrays before the for loop? Or have the for loop not die when it hits an empty array? Any help appreciated. Thanks.

The third element in data Array is an empty Array. So when your reach i=2 (which is the third element), data[i] is empty. So there is no `data[i][0] — matewka
– matewka, Commented Aug 29, 2013 at 13:33
check my answer it even checks for empty objects and arrays while being shortest — Muhammad Umer
– Muhammad Umer, Commented Aug 29, 2013 at 13:47
and i am pretty sure your syntax is wrong for declaring data array. you dont put object {..}. — Muhammad Umer
– Muhammad Umer, Commented Aug 29, 2013 at 13:56

SLaks · Accepted Answer · 2013-08-29 13:32:38Z

3

You can simply check whether the current item is empty:

if (data[i].length === 0) continue;

answered Aug 29, 2013 at 13:32

SLaks

891k182 gold badges1.9k silver badges2k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

suncoastkid Over a year ago

That's it... In this case it was !== 0. Thank you.

Tim Mac · Accepted Answer · 2013-08-29 13:40:32Z

0

Just wanted to add this as an answer.. In javascript, I believe null == false. So you can also do something like this:

if(data[i][0])
   //it's not null or undefined, do some work

answered Aug 29, 2013 at 13:40

Tim Mac

1,1491 gold badge9 silver badges17 bronze badges

Comments

OneOfOne · Accepted Answer · 2013-08-29 13:43:44Z

0

You need to make sure data[i] is an array and it has at least 1 item first :

var i, item, myarr = [],
    isNotEmptyArray = function(a) {
        return Object.prototype.toString.call(a) === '[object Array]' && a.length > 0;
    };

for (i = 0; i < data.length; i++) {
    item = data[i];
    if (isNotEmptyArray(item) && item[0].myvar) {
        console.log(item[0].myvar);
        dep = item[0].myvar;
        if (dep != null) {
            myarr.push(dep);
        }
    }
}

answered Aug 29, 2013 at 13:43

OneOfOne

100k22 gold badges194 silver badges187 bronze badges

2 Comments

Muhammad Umer Over a year ago

why create a monster like this when you can get the same result with data.forEach(function(e){ (e[0]) && myarr.push(e); });

OneOfOne Over a year ago

Not all browsers support forEach (well, mainly IE), I was just fixing his code.

0x_Anakin · Accepted Answer · 2013-08-29 13:44:31Z

0

for (var i = 0; i < data.length; i++) {
    if (data[i].length !== 0) continue;
    if (data[i][0].myvar) {
        dep = data[i][0].myvar;
        if (dep != null) {
            myarr.push(dep);
        }
    }
}

answered Aug 29, 2013 at 13:44

0x_Anakin

3,2695 gold badges52 silver badges90 bronze badges

Comments

Muhammad Umer · Accepted Answer · 2013-08-29 13:52:55Z

0

This is the best and cleanest way to do it.

data.forEach(function(e){
    if(Object.keys(e).length) myarr.push(e);
});

take a look http://jsfiddle.net/8zfZd/ open console to see object.

Object.keys()

forEach

to make it even shorter...

data.forEach(function(e){ (e[0]) && myarr.push(e); });

http://jsfiddle.net/cgg6j/

edited Aug 29, 2013 at 13:52

answered Aug 29, 2013 at 13:46

Muhammad Umer

18.3k26 gold badges111 silver badges179 bronze badges

Comments

fred02138 · Accepted Answer · 2013-08-29 13:37:36Z

-1

Add this loop before your loop to clear the empty arrays:

var i = 0;
while (true) {
    if (i == data.length)
        break;
    if (data[i].length == 0)
        data.splice(i, 1);
    else
        ++i;
}

answered Aug 29, 2013 at 13:37

fred02138

3,3611 gold badge16 silver badges18 bronze badges

4 Comments

matewka Over a year ago

Why looping twice? You can check if (data[i].length == 0) inside the same loop

fred02138 Over a year ago

@matewka The OP specifically asked for a way to remove the empty objects before the for loop. The code I supplied is tested and correct.

matewka Over a year ago

Though he asked, it doesn't mean it is correct. I think you could suggest a better answer than just fulfilling OP's request.

fred02138 Over a year ago

@matewka Ok, but consider that OP clearly didn't know how to remove elements of an array, so the answer may have value for him later even if he doesn't use it in this particular case.

Collectives™ on Stack Overflow

Working with empty objects in javascript array

6 Answers 6

1 Comment

Comments

2 Comments

Comments

Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

1 Comment

Comments

2 Comments

Comments

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related