Allow global configuration of XHR and XDR constructors

[mmacaula]

Came from conversation in #11, it would be nice to be able to configure the constructors of the XHR and XDR. From @Raynos:

require('xhr').set({
  XHR: function () { ... },
  XDR: function () { ... }
})

[dominykas]

Surely you'd also need a reset of some sort?

[Raynos]

Nope. your mutating the global state of the xhr library. It's your responsibility to set it back to the original state.

The use case for .set() is to overwrite the XHR constructor so that you can globally set some default headers or something.

[dominykas]

To restore the original state, one must be aware of what the original state is. Since both XHR/XDR are private via closure, there is no way to know the original state. Both contain initialization logic (noop, withCredentials, etc), so either both need to be exposed in public or there is a need to be able to reset them (could be done by passing in null to set - although I'm not sure that's a good contract).

Ofc, a much simpler solution would be to not keep them as global state and to simply move the construction inside the exported method... But we've been through that discussion...

[naugtur]

That's why I'd propose this:

var xhr = require('xhr')
xhr.internals.XHR = yourXHRmock

And that would be compatible with all sorts of mocking libs, like sinon

var stub1=sinon.stub(xhr.internals,"XHR")
stub1.restore()

And btw, I checked ampersand-sync and their package.json says xhr: ^1.10. I'm going to make a PR to migrate to 2.0 during the weekend (hopefully)

[Raynos]

@naugtur makes a good suggestion.

I would recommend xhr.XHR and xhr.XDR though.

[naugtur]

I thought xhr.XHR would be confusing for what it actually means.

BTW. Didn't make the PR to ampersand yet, waiting for the discussion to go somewhere.

[Raynos]

we can do xhr.XMLHttpRequest or xhr.XDomainRequest :D thats less confusing.

[naugtur]

Ok, one more thing - why XDR at all? If you mock XHR, you will surely mock it with an implementation that is in line with standards and therefore XDR is not needed. Or am I missing something?

[Raynos]

that's upto the user to decide. He can mock both or one.