Neat tool. Doesn't seem to be working for me, though (Firefox for Android, preview is stuck on "Loading")
Sorry about that. I was weighing the pro/con of waiting for support to be released or adding a polyfill but it seems that support is just around the corner from what I can tell from the issue.
[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... [2] https://github.com/mdn/content/issues/31098
Looks like a very good API, glad to have learned about it!
[1]: https://webkit.org/blog/11648/new-webkit-features-in-safari-...