SyntaxError: Unexpected token ‘'<'’ when fetching JSON response from Django API: A Comprehensive Guide to Troubleshooting

Ah, the infamous SyntaxError: Unexpected token ‘'<'’! You’re not alone, friend. Many developers have faced this frustrating issue when trying to fetch a JSON response from a Django API. But fear not, for we’re about to embark on a troubleshooting adventure that will leave you armed with the knowledge to conquer this error once and for all!

What’s causing the SyntaxError?

Before we dive into the solutions, let’s understand what’s causing this syntax error. The issue arises when your JavaScript code receives a response from the Django API that’s not properly formatted as JSON. This can happen for a variety of reasons, including:

• Incorrect MIME type specification in the Django API response
• Malformed JSON data
• Character encoding issues
• Improper use of templates in Django

Solution 1: Verify the MIME type

The first step in troubleshooting is to ensure that your Django API is returning the correct MIME type in the response headers. In your Django view, make sure you’re setting the `Content-Type` header to `application/json`:

from django.http import JsonResponse

def my_view(request):
    data = {'key': 'value'}
    return JsonResponse(data, content_type='application/json')

In your JavaScript code, verify that the response headers contain the correct MIME type:

fetch('/api/endpoint/')
  .then(response => response.headers.get('Content-Type'))
  .then(console.log); // Output: application/json

Solution 2: Inspect the JSON response

If the MIME type checks out, it’s time to inspect the JSON response itself. Use the browser’s developer tools or a tool like Postman to examine the response body. Look for any syntax errors or malformed JSON data.

If you’re using a template to render the JSON response in Django, ensure that you’re not accidentally injecting HTML tags into the response. Use a JSON-specific template like `application/json` or `json` instead of `html` or `txt`:

from django.template.loader import get_template

def my_view(request):
    data = {'key': 'value'}
    template = get_template('my_template.json')
    return HttpResponse(template.render(data), content_type='application/json')

Solution 3: Check character encoding

Character encoding issues can also cause the SyntaxError. Make sure that your Django API is returning the response with the correct character encoding. You can specify the encoding in the `HttpResponse` object:

from django.http import HttpResponse

def my_view(request):
    data = {'key': 'value'}
    return HttpResponse(json.dumps(data), content_type='application/json; charset=UTF-8')

In your JavaScript code, ensure that you’re not overriding the character encoding when parsing the response:

fetch('/api/endpoint/')
  .then(response => response.json())
  .then(data => console.log(data));

Solution 4: Review template usage

If you’re using templates in Django to render the JSON response, ensure that you’re not accidentally injecting HTML tags into the response. A common mistake is using a template with HTML tags and then trying to parse the response as JSON:

<!-- my_template.html -->
<div>{{ data }}</div>

Instead, use a JSON-specific template or render the JSON data directly in the view:

def my_view(request):
    data = {'key': 'value'}
    return JsonResponse(data)

Solution 5: Test with a JSON validator

If none of the above solutions work, it’s time to get out the big guns – a JSON validator! Use a tool like `jq` or an online JSON validator to test the response body:

$ curl -X GET 'http://localhost:8000/api/endpoint/' | jq .
parse error: Invalid literal at line 1, column 1

If the validator returns an error, it’s likely that the response body contains malformed JSON data. Review your Django view and templates to ensure that you’re generating valid JSON.

Conclusion

There you have it, folks! With these solutions, you should be able to troubleshoot and resolve the SyntaxError: Unexpected token ‘'<'’ when fetching a JSON response from a Django API. Remember to:

1. Verify the MIME type
2. Inspect the JSON response
3. Check character encoding
4. Review template usage
5. Test with a JSON validator

By following these steps, you’ll be well on your way to resolving this pesky error and enjoying a smooth JSON experience. Happy coding!

Solution	Description
Verify MIME type	Ensure the Django API response has the correct MIME type (application/json)
Inspect JSON response	Verify the JSON response body is valid and doesn’t contain syntax errors
Check character encoding	Ensure the correct character encoding is specified in the response headers
Review template usage	Ensure templates are not injecting HTML tags into the JSON response
Test with JSON validator	Use a JSON validator to test the response body for syntax errors

Frequently Asked Question

Having trouble fetching JSON response from your Django API? Don’t worry, we’ve got you covered! Here are some FAQs to help you troubleshoot that pesky SyntaxError.