Error: Can't set headers after they are sent to the client-Resolved

The error “Can’t set headers after they are sent to the client” occurs when you try to set a response header after the response has already been sent to the client. This can happen if you have multiple res.send(), res.json(), or res.redirect() statements in your code, or if you’re trying to set a header after a response has already been sent.

To resolve this issue, make sure that you only call res.send(), res.json(), or res.redirect() once in your code, and you set all the necessary headers before sending the response.

Here’s an example of how you can resolve this issue in an Express.js application:

app.get('/', function (req, res) {
  res.setHeader('Content-Type', 'text/html');
  res.status(200).send('<h1>Hello World!</h1>');
});

In this example, the Content-Type the header is set before the response is sent to the client, which eliminates the possibility of the “Can’t set headers after they are sent to the client” error.

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