Question

15

Check if object key exists within object

rated 0 times [ 16] [ 1] / answers: 1 / hits: 80706 / 11 Years ago, fri, september 20, 2013, 12:00:00

I'm trying to take some data from an existing object and group it into a new one. The problem I am having is checking if the object key exists so I can either create a new one, or append data to an existing one.

I've found a few similar questions but none of the answers worked so I'm a bit stuck. It always ends up finding it doesn't exist and creating duplicate keys.

I have the following code, where xxx is where I need to check if the key exists:

var groups = [];    



for (var i=0; i<something.length; i++) {



    var group_key = 'group_'+something[i].group_id;



    if (xxx) {



        // New group



        var group_details = {};



        group_details[group_key] = {

                group_name: something[i].group_name,

                items:  [

                    { 'name': something[i].name }

                ]

        };

        groups.push(group_details);



    } else {



        // Existing group



        groups[group_key].items.push({

            'name': something[i].name

        });



    }



}

The something I am passing in, is pretty simple, basically in the form of:

[

    {

        group_id: 3,

        group_name: 'Group 3',

        name: 'Cat'

    },

    {

        group_id: 3,

        group_name: 'Group 3',

        name: 'Horse'

    },

    {

        group_id: 5,

        group_name: 'Group 5',

        name: 'Orange'

    }

]

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jeremiahianx

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2 Years ago

answered 11 Years ago mckinley · Accepted Answer

The best way to achieve this would be to rely on the fact that the in operator returns a boolean value that indicates if the key is present in the object.

var o = {k: 0};



console.log('k' in o); //true

But this isin't your only issue, you do not have any lookup object that allows you to check if the key is already present or not. Instead of using an array, use a plain object.

var groups = {};

Then instead of groups.push(...), do groups[group_key] = group_details;

Then you can check if the group exist by doing if (group_key in groups) {}