No you don't. You export it as png or whatever
lossless format you can and your job here is pretty much done. Then technical guys you are working with convert it or write a script to convert it automatically on upload/download on their website or do whatever they need to do to get lossy image for whatever purposes.
Still, to become truly widespread you need to have support in all kinds of software out there, "everything you need is js plugin" is unreasonable optimism in my opinion. And, anyway, decoding using js isn't fast enough to be one and only solution forever, you need to get to have browser and other software support sooner or later, and for that you need 1 standardized format, not "whatever your plugin supports" as thread-starter suggests.