> Don't get me started with conflating http server errors with applications errors.
I've wasted so much time dealing with 404 errors that were returned by the webserver itself (not the app) because the endpoint I was hitting was wrong or had moved, and vice-versa when I was correctly hitting the app but got a 404 error back from the API and I thought that the endpoint was wrong. And, of course, similar issues for 500 errors and the app itself dying versus the app processing normally and indicating an expected failure response via a 500 error code.
To add to all that badness, a lot of JS libraries in their async API method calls have different error handlers for success and for failure response codes, so you end up having to lump together business logic (for resources not found) and retry/error-handling logic (for the server the not working correctly) into the same failure response callback handler. It'd be much cleaner if all the business logic could be handled in a single callback and all of the failure logic could be handled in another. And, of course, you only even get to this level of badness once you figure that out; you can still waste quite a bit of time before you even realize that your callback is not being called because the JS framework is interpreting the expected 404 your API endpoint is returning for non-existent things in business logic differently than you are.
I still wouldn't go back to SOAP, but I do tend to prefer HTTPS/JSON-based APIs that don't abuse verbs, HTTP error codes, and mixes of URLs/params/headers/payloads. Better to put all of that stuff inside the JSON payload where it will only be handled by the application business logic, rather than mixing it in with all of the HTTP constructs that are used for other things as well.