Why Do I Get \'Unexpected End of Input\' Errors When Handling \'no-cors\' Fetch Responses?

Handling Response - Unexpected End of Input Error with 'no-cors' Mode

When using 'no-cors' mode in a fetch request, you may encounter a "SyntaxError: Unexpected end of input" when attempting to handle the response. This error is caused by the opaque nature of no-cors requests, which prohibits frontend JavaScript from accessing the response body or headers.

Cause of the Error

By setting the mode to 'no-cors', you instruct the browser to block frontend JavaScript access to the response, regardless of the response status code or presence of Access-Control-Allow-Origin headers. This prevents JavaScript from parsing the response JSON and leads to the unexpected end of input error when calling response.json().

Solution

To resolve this error, remove the 'no-cors' mode setting from your request. If you need to make cross-origin requests, consider the following solutions:

• Configure the Server: Enable CORS by setting the Access-Control-Allow-Origin header on the server-side and ensuring it handles OPTIONS preflight requests.
• Use a CORS Proxy: Utilize a CORS proxy to forward requests and hide cross-domain issues. Popular options include cors-anywhere (https://github.com/Rob--W/cors-anywhere/) and other similar services.

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