I have an empty json object like this

var image, description ;

var json = { 0 : { image : " " , description : " " } };

I want to populate like this by looping through n but this way of adding properties it gives be this error : "cannot set property description of undefined"

json[n].description = " nth description";
json[n].image =   " nth image";

In the end I want var json to be like this

var json = { 0 : {"image" : "1st image", "description" : "2nd description"  }
             1 : {"image" : "2nd image", "description" : "2nd description" }
             2 : {"image" : "3rd image ", "description" : "3rd description" }
             3 : {"image" : "4th image ", "description" : "4th description" }
}

and so on .... I get the undefined error on the first iteration so I haven't even attempted adding the second or third elements yet so not sure if that would need something else.

I have an empty json object like this

var image, description ;

var json = { 0 : { image : " " , description : " " } };

I want to populate like this by looping through n but this way of adding properties it gives be this error : "cannot set property description of undefined"

json[n].description = " nth description";
json[n].image =   " nth image";

In the end I want var json to be like this

var json = { 0 : {"image" : "1st image", "description" : "2nd description"  }
             1 : {"image" : "2nd image", "description" : "2nd description" }
             2 : {"image" : "3rd image ", "description" : "3rd description" }
             3 : {"image" : "4th image ", "description" : "4th description" }
}

and so on .... I get the undefined error on the first iteration so I haven't even attempted adding the second or third elements yet so not sure if that would need something else.

• javascript
• json
• node.js

• In the console it is working fine for me... May be you are iterating even when other element hasn't been created ... Instead you should make a child object and push it to an array instead of this json type object. Something like this : var json = [ {image : , description : }] – binariedMe Commented Jul 16, 2015 at 9:49

3 Answers 3

Because in your example, if n is anything else than 0, the object is undefined.

Create the empty object before using it :

json[n] = {};
json[n].description = " nth description";
json[n].image = " nth image";

You can do it like this :

var json =  {}
json[n] = {}
json[n].description = " ....."
json[n].image = " ..... "

You need to create the new object inside the original and then declare its properties.

you can code like this.

var nt = ['st', 'nd', 'rd', 'th', 'th', 'th', 'th', 'th', 'th', 'th'];
var json = {};
for(var i=0;i<n;i++) {
        var tp = json[i]  = {}; //define first if it a object otherwise it say undefined.
        tp['image'] = i+nt[(i%10)]+' image';

        tp['image'] = i+nt[(i%10)]+' description';
    }
    console.log(json);