Refactor defaults

[simov]

This is a follow up to #1518

Much more simplified defaults and params initialization in index.js. Basically flattened the logic, also moved the wrap closure outside of the defaults method and I left it in index.js because I think it's very closely related to the request method, and the convenience http verb methods. Also completely dropped all of the object extend closures, as I don't think they add any substantial value to that piece of code.

/cc @nylen @FredKSchott @mikeal

[FredKSchott]

wrap is a little vague, it took me a while to understand what this function was doing. Is there a better name here that could provide a little more context? wrapDefaults? wrapRequestMethods?

Also, some documentation on expected arguments would be equally helpful, especially since it looks like we support a lot of different ways to call this (method = string, function, or request, request is optional, etc).

[FredKSchott]

👍 with comments

[simov]

I managed to squeeze the code a bit further by removing redundant data structure returned by initParams

Regarding your comment @FredKSchott about passing a string to the wrapRequestMehod function, I can't figure out a good way to remove the string parameter from there without introducing complexity in another place.

The reason for passing string there is to be able to set the params.method which is later used in the request function to abort the request on HEAD + body.

Similar to the way the http verb methods set the method name after calling initParams, the wrapRequestMethod is doing exactly the same, again after the initParams was called.

Here is the catch - on wrapped http verb method + requester, the default http verb method is never called, because the requester takes precedence. Therefore the request method is never set, so the request can't be aborted in the request function (and we have a test for that too).