How to Fix the 'Error: Can't set headers after they are sent to the client' in Node.js?

Guide to resolve "Error: Can't set headers after they are sent to the client" issue

When you call res.redirect (), the response status in Connect/Express changes to Finished. Following the recommended approach, you cannot set further headers or set errors while the response is in the completed state.

Ways to avoid errors

To avoid this error, follow these best practices:

• Before setting headers and responding Handle errors before.
• Use appropriate Connect/Express middleware to handle errors, such as error-handler.
• Make sure no data is sent before calling res.redirect().

Error Analysis

In this case, the error occurs after the res.redirect() call. Connect/Express attempts to send a 500 error page, but because the headers have already been sent, the error is thrown.

Other Notes

Please note that the order of Connect/Express response methods is important. Be sure to start with the head and continue with the body and finish accordingly. Please refer to the following guides for details:

https://expressjs.com/en/4x/api/#res.end

By following these best practices, you can avoid "Error: Can't set headers after they are sent to the client" error occurs in Connect/Express application.

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