zlacker

But wouldn't responseStatus === 4xx indicate that the problem is on your end and retrying is unlikely to fix the issue. A 5xx is worth a retry, a 4xx should imho just produce an error message.

And even if you do retry, exponential backoff has been the standard for a long time (and is mentioned by the Twitter API documentation as a good solution to 429 responses)

>>wongar+(OP)
There are libraries, usually under the general heading of "circuit breaker", that handle 429 and other reasons to retry in a sane manner. I'm not a JS expert but I believe either yammer/circuit-breaker-js or nodeshift/opossum would work in the browser. Even a hand-coded exponential backoff with jitter is simple enough to do for most cases.