Consideration of removing non-standard methods

[Bhpsngum]

In the current code, some methods are not standard per W3C spec:

• .getRequestHeader(header_name): Get any request header
• .setDisableHeaderCheck(): Allow all forbidden headers to pass through and set to the request header

I'm planning to clean them up on my next PR, along with some other changes discussed in recent issues, but seeing the amount of usage in test case files, now I wonder if we need to remove them because of a non-standard spec? Or can we keep it, but specify another flag to explicitly enable them?

I'm looking forward to your opinion.

[mjwwit]

Apologies for my tardy response, I've been under the weather for the past few days.

I'm all for removing non-standard methods, but we should ensure we're not removing any functionality.
I think .setDisableHeaderCheck() could be an (admittedly still non-standard) constructor option. This approach would allow maintaining of current functionality while also allowing for browser compatibility (calling an unsupported method on an XHR instance will throw, but passing non-standard options to the XHR constructor is allowed).
However, I don't think this approach will work for .getRequestHeader(header_name). I really can't see a need for this method to exist though, as it should be rather easy to track request headers on the side if you really want to. If it's used extensively in the test files we can first deprecate it by adding a jsdoc @deprecated comment and a warning log (this one doesn't need a config flag to disable IMO). We can then remove it in a later release.

[Bhpsngum]

That sounds good to me, i'll include it in my later PR too

[mjwwit]

Fixed (partially deprecated) in #31, released as 4.0.0