Destructure / Easy Object Composition

Yes, you're right - there's no support at the moment. Generally the state of language support is on the http://www.espruino.com/Features page as Robin says.

However nothing stops you from transpiling your JS code into something else. For instance if you go to Minification in settings and turn it to Closure (online) - Simple Optimisations you can then use destructuring.

There's a wishlist here which you can vote on: https://github.com/espruino/Espruino/iss­ues/1302

And generally I do try and add the most requested features when I get time :)