How to Fix \'SyntaxError: Unexpected end of Input\' in React Fetch Calls?

Unexpected End of Input: Resolving SyntaxError with Fetch Call in ReactJS

When attempting to handle a response from a REST API call using ReactJS, you may encounter the following error:

SyntaxError: Unexpected end of input

This error often occurs when using the mode: 'no-cors' setting in your fetch request.

What is CORS (Cross-Origin Resource Sharing)?

CORS is a security mechanism that prevents scripts from different origins (i.e., different websites or URLs) from accessing and modifying resources on other origins. It ensures that unauthorized scripts cannot steal or manipulate data from other websites.

Why 'no-cors' Mode Causes Issues

By setting mode: 'no-cors', you explicitly tell the browser not to perform any preflight request or send CORS headers. This means that the response from the server will be opaque to your frontend JavaScript code.

How to Resolve the Error

To resolve the error, you need to remove the mode: 'no-cors' setting from your fetch request. This will allow the browser to send the necessary CORS headers and handle the response appropriately.

Alternate Solutions

If you are unable to remove the mode: 'no-cors' setting due to server configuration or limitations, consider using one of the following workarounds:

• Configure the Server:

  • Update your server configuration to send the Access-Control-Allow-Origin response header, allowing frontend JavaScript code from other origins to access the response.

• Use a CORS Proxy:

  • Set up a CORS proxy using services like cors-anywhere to bridge the gap between your frontend code and the target server.

By following these recommendations, you can effectively handle responses from REST API calls in ReactJS, avoiding the "Unexpected end of input" error caused by the mode: 'no-cors' setting.

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