The problem being that browser vendors tend to implement Web APIs early, before the API and the respective specifications are frozen and are still likely to var

The problem being that browser vendors tend to implement Web APIs early, before the API and the respective specifications are frozen and are still likely to vary. They may even implement a certain (still valid) interpretation of the specs, which then turns out to be not exactly what everybody else eventually implements, but may stick to this for some time. (There are examples for about every browser vendor on the planet for this. Without this, if everybody had waited for finalized specs, we wouldn't have web sockets, web databases, or Web RTC for years now.) How do you handle this without version numbers?