Javascript object from json file, array inside object is undefined

Question

I'm trying to access some data which is in a json file. I read the data through AJAX and try to traverse through the data.

Here's my json file. {"data":[{"LotNo":"1", "UnitNo":"1"}, {"LotNo":"2", "UnitNo":"2"}]}

And the function in my html file.

function X1(){

        var xmlhttp = new XMLHttpRequest();
        xmlhttp.onreadystatechange = function() {
            if (this.readyState == 4 && this.status == 200) {
                var myObj = JSON.parse(this.responseText);
                X2(myObj);   
            }
        };
        xmlhttp.open("GET", "test.txt", true);
        xmlhttp.send();         
    }

And the function in the same file which uses the object.

function X2(obj)
    {
       var dataObject = JSON.stringify(obj);
       alert(dataObject.length);                      //Gives me 64 
    }

Why does it give me 64?

Why can't I access the data array like this?

alert(dataObject.data.length);

Or

alert(dataObject.data[0]);

It gives me the error that 'data' is undefined.

How can I get to the elements of this array?

You're parsing JSON and then stringifying it again. One of these steps is not necessary. — georg
– georg, Commented May 25, 2021 at 10:46
Hi, stringifying the Json, converts the obj into a string, and when calling length it returns 64, the length of the string. As said by @georg, remove method JSON.stringify. — Yash Maheshwari
– Yash Maheshwari, Commented May 25, 2021 at 10:49
It looks you don't need to use Ajax. You can straight-a-way read it from the file. — Rajdeep D
– Rajdeep D, Commented May 25, 2021 at 10:51

Jeroen Rinzema · Accepted Answer · 2021-05-25 10:50:51Z

1

JSON.parse parses the given input and attempts to convert it into a JSON object. Which is passed to JSON.stringify inside the X2 method. JSON.stringify encodes the decoded JSON object into a string. The encoded JSON object is 64 characters long instead of 67 characters because JSON.stringify removes the spaces inside the received JSON object.

If you want to access the content in the object remove JSON.stringify. You are able to access properties inside the object since you decoded it already using JSON.parse.

var myObj = JSON.parse(this.responseText);
console.log(myObj.data[0].LotNo)

answered May 25, 2021 at 10:50

Jeroen Rinzema

901 silver badge4 bronze badges

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

Comments

ASC Developers · Accepted Answer · 2021-05-25 11:47:31Z

1

JSON.stringify(obj)

Remove JSON.stringify() as it converts an object to JSON. You are already parsing the json in your ajax call.

var dataObject = JSON.stringify(obj);

Remove this line and try

obj.data.length

edited May 25, 2021 at 11:47

answered May 25, 2021 at 10:52

ASC Developers

115 bronze badges

Collectives™ on Stack Overflow

Javascript object from json file, array inside object is undefined

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related