NodeJS request module - body on http.IncomingMessage?

Question

I'm looking into the node's request module, and documentation says that callback accepts three params - error , response ( http.IncomingMessage ) and body .

When making a request, I found that body also available as a property on the response object.
Is that reliable? Can I just omit last param in the callback and use response.body instead?

Answer 1

response.body is not always the same as the body argument. If any processing is requested on the response such as decompression, then the body argument will be the result of that processing, but response.body may not reflect that processing. You should use the response argument. Here's one example from the documentation:

For backwards-compatibility, response compression is not supported by default. To accept gzip-compressed responses, set the gzip option to true. Note that the body data passed through request is automatically decompressed while the response object is unmodified and will contain compressed data if the server sent a compressed response.

Answer 2

Yes, body is just a convenience for response.body so they are guaranteed to always be the same.

You can verify this by checking the source code .

self.emit('complete', response, response.body)

and elsewhere in the same file the complete event is handled

self.on('error', self.callback.bind())
self.on('complete', self.callback.bind(self, null))

This is only true of the response passed to the callback. The response object passed to the response event is a standard http.IncomingMessage and as such has no body property.