_example.js

// You can chain a list of this type of "chainable" http function with "callback hell"
chainA({ cb: (results) => 
  chainB({ results, cb: () => 
    chainC({ cb: (results) => 
      chainD({ results }) 
    }) 
  }) 
})

// But I want a helper with this API:
chain(chainA, chainB, chainC, chainD)

chainable-examples.js

import { http } from './http'

// example of a "chainable" http method
function isChainable({ results, cb, ...rest }) {
  const args = {} // may or may not use results and/or rest to construct http args
  args.cb = cb;
  http(args)
}

http.js

// the baseline magic http method, e.g.
export function http(args) {
  // does stuff with args
  return makeHttpRequest(args)
    .then((results) => {
      if (args.cb) {
        cb(results)
      }
    });
}