CODEWITHSUNDEEP
javascriptarrays
suncoastkid
suncoastkid

Reputation: 2223

Working with empty objects in javascript array

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.

Upvotes: 1

Views: 161

Answers (6)

Muhammad Umer
Muhammad Umer

Reputation: 18097

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/

Upvotes: 0

0x_Anakin
0x_Anakin

Reputation: 3269

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);
        }
    }
}

Upvotes: 0

OneOfOne
OneOfOne

Reputation: 99224

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);
        }
    }
}

Upvotes: 0

Tim Mac
Tim Mac

Reputation: 1149

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

Upvotes: 0

fred02138
fred02138

Reputation: 3361

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;
}

Upvotes: -1

SLaks
SLaks

Reputation: 887385

You can simply check whether the current item is empty:

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

Upvotes: 3

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