Can someone explain how chained functions work when there is a prototype function in the chain in JS?

Question

I'm trying to separate the chained calls from:

request
  .post('/upload')
  .attach('image1', 'path/to/felix.jpeg')
  .attach('image2', imageBuffer, 'luna.jpeg')
  .field('caption', 'My cats')
  .end(callback);

to:

request
  .post('/upload')

request
  .attach('image1', 'path/to/felix.jpeg')
  .attach('image2', imageBuffer, 'luna.jpeg')
  .field('caption', 'My cats')
  .end(callback);

I'm probably thinking about this wrong and missing a concept, but I would like to know why that doesn't work and how does .attach (being a function added to the prototype of request) does get called in the first instance. And any pointers to any resources

Ref: https://github.coventry.ac.uk/askaria/304CEM-LizoFile/blob/master/node_modules/superagent/docs/index.md#attaching-files

https://github.com/visionmedia/superagent

Answer 1

The request.post() call is actually returning something and then the next method .attach() is called on that returned data.

You can use

const req = request
  .post('/upload');

req
  .attach('image1', 'path/to/felix.jpeg')
  .attach('image2', imageBuffer, 'luna.jpeg')
  .field('caption', 'My cats')
  .end(callback);