I like it, but idiomatic symbols are tough. When I look at some functional languages they seem so dense with operators that I have to use some inference (which I probably get at least partially wrong) to glean the meaning. This is a good operator that, in my opinion, should be in a dynamically-typed object-oriented language. But it is not as universally understood as most of JavaScript.
There is a place for languages that use more keywords and fewer operators as a design choice. Of course there also need to be languages that don’t have the undefined/null value and don’t need this.
> What happens when the browser supports an operator the version of Typescript you are using doesn't?
Nothing, because the compiled TypeScript won't contain it. TypeScript is deliberately conservative about the language features it supports to ensure it never gets out of sync with JS.
There is a place for languages that use more keywords and fewer operators as a design choice. Of course there also need to be languages that don’t have the undefined/null value and don’t need this.