[TheAceOfHearts]

I think this kind of access pattern is typically a code smell. Instead of carrying around arbitrarily nested values you should try to normalize it into a known and consistent shape when crossing serialization boundaries.

Proxy pays a big performance penalty, and I doubt it'll be improving any time soon. In addition, I believe it's not possible to polyfill Proxy. An alternative could be to just wrap the deep property access in a try/catch:

    function getQux (input) {
      try {
        return input.foo.bar.baz.qux()
      } catch (e) {
        return null
      }
    }

[afranchuk]

Yeah, my first thought when seeing that it uses Symbol and Proxy was that Proxy can't be polyfilled. But it looks like there's partial polyfills for it: https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...

[slmgc]

Wrapping you code into a try/catch block decreases performance even more, you don't want to do that. You might want to check it out: https://github.com/GoogleChrome/proxy-polyfill