Unexpected Token F in Json at Position 192 Try Againchoose File

In this article you will larn what JSON is and how you can deal with errors occurring when parsing JSON data, such equally "Unexpected Token < in JSON at Position 0."

What Is JSON

JSON, which is an acronym for JavaScript Object Notation, is one of the nigh popular data formats used for transmitting data. Information technology is a lightweight format and consists of proper noun-value pairs. Values can be strings, arrays, or any other data that can be serialized.

In the sometime days XML was primarily used for interchanging data, but since JSON appeared information technology is often used equally a replacement of XML. A JSON file should end with the.json extension.

Beneath yous tin see an example of a JSON format.

                      {            "name"            :            "animals"            ,            "animals"            :            [            "Dog"            ,            "Cat"            ,            "Mouse"            ,            "Pig"            ,            "Bear"            ]            ,            "hobbies"            :            {            "football"            :            false            ,            "reading"            :            truthful            }            }                  

JSON format is quite similar to JavaScript objects, but information technology is not ever the case. It is important to think that every belongings name must exist wrapped in double quotes.

                      // not valid JSON            {            x:            4            }            // valid JSON            {            "x"            :            iv            }                  

Unexpected Token < in JSON at Position 0

From time to time when working with JSON data, you might stumble into errors regarding JSON formatting. For instance, if you try to parse a malformed JSON with theJSON.parse() function or utilize the.json() method on the fetch object, it can result in a JavaScript exception being thrown. Simply don't worry, it'southward not the end of the world and we tin handle it. There can be dissimilar causes for this happening then let's see what we can do almost information technology.

Is My JSON Formatted Correctly?

Projects sometimes require configuration that is sent to the customer from a server. Only and then you know, storing the config details every bit a JSON will exist faster than using an object literal, as engines demand to practise more steps when running an object literal than JSON.parse(), for instance. The operation comparison of JSON vs JavaScript is not a topic of this article so information technology volition non be covered, but if you lot are interested, then yous can read more most it here.

If y'all accept a file with JSON data, i of the commencement things to practice is to ensure that the data is formatted correctly. There are a few sites that can assist yous with that. These formatters non but volition check if your JSON is formatted correctly, simply they tin too fix some of the errors, beautify it, or make it meaty.

• https://jsonformatter.org/
• https://jsonformatter.curiousconcept.com/
• https://codebeautify.org/jsonvalidator

To be honest, one of the mistakes I am often guilty of myself is using single quotes instead of double quotes. The paradigm below shows how a format checker can make your life easier.

If your JSON is formatted correctly, then it is time to check what else could be wrong.

My JSON is Formatted Correctly—What Next?

"Unexpected token < in JSON at position 0" is the error that I have seen most throughout my time of working as a software developer. Quite ofttimes it happens in a situation when fetch role is used for sending an API request from a client. After receiving a response from a server, unremarkably it is parsed to JSON.

                      fetch            ('url')            .            then            (response            =>            response.            json            (            )            )                  

The first matter to do in this situation is to confirm where the error is happening exactly. To ensure the error happens on the exact line we call up information technology does, nosotros can wrap the JSON parsing code in a try-catch block. Bank check the code below.

                      fetch            (            "url"            )            .            and then            (            async            response            =>            {            try            {            const            data            =            await            response.            json            (            )            console.            log            (            'response data?'            ,            data)            }            catch            (error)            {            console.            log            (            'Error happened here!'            )            panel.            fault            (error)            }            }            )                  

If this is the culprit, then information technology will exist clearly visible in the developer tools console, every bit "Error happened here!" will be displayed. Otherwise, you might need to wait for it somewhere else. A adept idea is to sometimes comment out code piece past piece to run across when an fault stops being thrown. You lot can besides use an early return argument.

The side by side pace is to check if the data we are expecting to meet is really being sent from the server. As shown on the epitome below, head to the "Network" tab in DevTools, discover the request, and click on the "Response" tab.

In this case, we can run across a JSON string sent from the swapi API, then it is correct. However, in a different case, the response could be in the XML format or the server could have sent an HTML file. The former could happen if yous are dealing with a server that tin render different responses depending on the content-type header provided. If this is the example, when you ship a asking, make certain yous specify the content-blazon header equally shown below:

                      fetch            ('url',            {            method:            'GET',            headers:            {            'Content-Blazon':            'application/json'            }            }            )            .            then            (response            =>            response.            json            (            )            )                  

As for the latter, I have seen the server sending an HTML file on a few occasions. Usually, a reason for this was an incorrect URL provided to the fetch method, or the API server route was not prepare correctly. For example, if you take a Unmarried Page Application and a backend running Limited.js server, it could be set up to always serve an index.html file. Therefore, ever double-cheque your URLs and API routes configuration.

Conclusion

JSON is an extremely popular format and is unremarkably used for information interchanging. We have talked about what JSON is, and what we can do when a parsing error is thrown. For starters, always double-check if the values you are dealing with are what y'all look them to exist, and retrieve, console.log() is your friend.

arkwookerumtraturness.blogspot.com

Source: https://www.telerik.com/blogs/what-is-json-how-to-handle-unexpected-token-error

Share this post