Certain experimental features haven't been added to Firefox's Javascript engine. In your example, the pipeline operator hasn't been added to any browser yet because it's still in its very early stages.

You'd need to use a compiler like Babel to convert your experimental code into regular Javascript that can be understood by Firefox.

For example, Babel has a web-based compiler where you can convert your code into regular Javascript.

Hope this helps.

Thank you Wesley. I don't know which of the firefox experimental technologies does Babel convert to javascript.

Though it would be nice for firefox developer ed. to do it.

Firefox Developer Edition isn't hugely different from Firefox Beta. It is a version ahead of the standard Firefox release, which allows you to test future features that are coming to Firefox. It also has a few useful developer tools that you can use. The other big difference is that it runs on it's own profile, so your settings and add-ons in the standard Firefox aren't impacted by what you do in the Firefox DE.

Other than that, it runs off of the same engine as Firefox Beta. The experimental features that you are looking to explore are far too early into the process. For example, the pipeline operator is only in stage 1 (which is just a proposal). Typically, a feature won't be added to the Firefox Javascript engine until the stage 2 (draft) or stage 3 (candidate) area.

Including them into the engine before that point could mean a lot of overhead for the Firefox developers, since experimental features often undergo a lot of changes before they are ready for release.

Thank you Wesley.