I worked out how to do this with an invisible 0-size frame, over 10 years ago. From another frame, you put data in the invisible frame (in a form, or as an URL) and submit it; then read the data back. Of course, it was awkward, and maybe there were some cross-browser issues (I don't recall, but such issues were the norm).
But here's my point: I thought it was technically cool, but I didn't do anything with it. Not even a demo. So this is a striking example for me that it really matters how familiar you are with a concept, before you can start using it as a basis of inventing something else. Progress takes a long time, and proceeds in steps. There's a tantalizing possibility that, maybe, knowing this could give you a simple way to leapfrog a decade ahead...
But here's my point: I thought it was technically cool, but I didn't do anything with it. Not even a demo. So this is a striking example for me that it really matters how familiar you are with a concept, before you can start using it as a basis of inventing something else. Progress takes a long time, and proceeds in steps. There's a tantalizing possibility that, maybe, knowing this could give you a simple way to leapfrog a decade ahead...