Getting null value in an array

Question

I have a default JSON file :-

{
    "_name":"__tableframe__top",
    "_use-attribute-sets":"common.border__top",
    "__prefix":"xsl"
}

I am trying to push some value by creating an array , but I am getting my array undefined value after pushing the data

{
    "_name":"__tableframe__top",
    "_use-attribute-sets":"common.border__top",
    "__prefix":"xsl",
    "attribute":[undefined]
}

First I am checking if the object contains array or if not then create the array. And if if already an array is there then do nothing.

    if(!($scope.tObj.stylesheet["attribute-set"][4].attribute instanceof Array)){
        const tableframe__top_content = $scope.tObj.stylesheet["attribute-set"][4].attribute;
        $scope.tObj.stylesheet["attribute-set"][4].attribute = [tableframe__top_content];
 }

After this , I am checking if attribute with _name = something is already there or not in the array. If not then push.

var checkTableFrameTopColor = obj => obj._name === 'border-before-color';
        var checkTableFrameTopWidth = obj => obj._name === 'border-before-width';

        var checkTableFrameTopColor_available = $scope.tObj.stylesheet["attribute-set"][4].attribute.some(checkTableFrameTopColor);

        var checkTableFrameTopWidth_available = $scope.tObj.stylesheet["attribute-set"][4].attribute.some(checkTableFrameTopWidth);

        if( checkTableFrameTopColor_available === false && checkTableFrameTopWidth_available  === false ){
            $scope.tObj.stylesheet["attribute-set"][4].attribute.push({
                    "_name": "border-before-color",
                    "__prefix": "xsl",
                    "__text": "black"
                    },{
                    "_name": "border-before-width",
                    "__prefix": "xsl",
                    "__text": "1pt"
                     }
                     );
            console.log("pushed successfully");     
            console.log($scope.tObj);       
        }

I am getting null value on array and an error TypeError: Cannot read property '_name' of undefined at checkTableFrameTopColor.

Where am I going wrong ?

EDIT:-

Like this I want to achieve-

{
    "attribute":[
                    {"_name":"font-weight","__prefix":"xsl","__text":"bold"},
                    {"_name":"color","__prefix":"xsl","__text":"black"}
                ],
    "_name":"__tableframe__top",
    "_use-attribute-sets":"common.border__top",
    "__prefix":"xsl"
}

some one told me to use square brackets just now may help? my question just now — zip
– zip, Commented Feb 4, 2019 at 11:28
go to the developer tools of your browser and check the value of obj — Fakhar Ahmad Rasul
– Fakhar Ahmad Rasul, Commented Feb 4, 2019 at 11:32
Try creating a JSFiddle with your code and post the link here — Maurício Araldi
– Maurício Araldi, Commented Feb 4, 2019 at 11:32
@zip No , in the above code if "attribute": { }is an object and is present in the main json object then it will turn to array. But there attribute is not present from begining — WhoAmI
– WhoAmI, Commented Feb 4, 2019 at 11:32
@FakharAhmadRasul I have already mentioned in the question. Getting { "_name":"__tableframe__top", "_use-attribute-sets":"common.border__top", "__prefix":"xsl", "attribute":[undefined] } — WhoAmI
– WhoAmI, Commented Feb 4, 2019 at 12:00

Christoph Lütjen · Accepted Answer · 2019-02-04 12:14:36Z

1

I have to guess but let me post it as an answer so I can use formatting…

Given:

const input = {
    "_name":"__tableframe__top",
    "_use-attribute-sets":"common.border__top",
    "__prefix":"xsl"
}

Note: Value of input.attribute is undefined.

    if(!($scope.tObj.stylesheet["attribute-set"][4].attribute instanceof Array)){
        const tableframe__top_content = $scope.tObj.stylesheet["attribute-set"][4].attribute;
        $scope.tObj.stylesheet["attribute-set"][4].attribute = [tableframe__top_content];
 }

.. so if this input is what you access in your if statement

input.attribute instanceof Array => false

it will be true and your code block will be executed and it says:

const example.attribute = [input.attribute]
// example.attribute == [undefined]

If I understand you correctly, you could solve it like so:

$scope.tObj.stylesheet["attribute-set"][4].attribute = (!tableframe__top_content) 
    ? [] 
    : [tableframe__top_content];

If attribute value could be false, you'd have to check with tableframe__top_content === undefined || tableframe__top_content === null.

edited Feb 4, 2019 at 12:14

answered Feb 4, 2019 at 12:03

Christoph Lütjen

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3 Comments

WhoAmI Over a year ago

Your logic is correct. Even I thought so but it is showing the same error. You mean like this if(!($scope.tableObj.stylesheet["attribute-set"][4].attribute instanceof Array => false)) ?

Christoph Lütjen Over a year ago

I updated the answer and added a suggested solution (before I just described why you see this error).

WhoAmI Over a year ago

Ok , Yes I got it. Thanks for the solution. It works .

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