只有html和javascript才能实现持久、可共享的存储?

Edit: Let me try to clarify with a use case. I would love to be able to run a simple chat-box on an html/javascript page without running my -own- server. I can write the chat application's javascript just fine, but don't have a solution that allows me to store the data to make the chat messages visible to all browsing users. So my app would accept data, post it to a third-party data store (Ideally just in json format), and poll from the data store for updates periodically. That's not the only thing I would use such a json storage service/json storage engine for, but it is the clearest example. Let me try to clarify with a use case. I