I don't see how syntactic sugar makes any sense for javascript. Breaking compatibility is so severe because every browser needs to catch up, yet it doesn't actually enable anything that couldn't be done before.
It lets a transpiler like Babel or Typescript use the new syntax and output the equivalent code that works on older browser.
Same reason async/await was useful far before there was native browser support - you could immediately use it in your codebase and compile to a legacy browser target.
If you're compiling to javascript anyway, why would you need a pipe operator in javascript instead of just nesting the function calls?
Because x |> f |> g |> h is much easier to read than h(g(f(x))) for most people.
If you're compiling from another language you would be using whatever syntactic sugar you want, why break compatibility just to have the compiled javascript look a little better?
> If you're compiling from another language
TypeScript isn't another language though. It is the latest official ECMAScript plus type annotations. Only some very, very few, rare, old stuff like enums really is different code. 99% of TypeScript is just "remove the types to get ECMAScript".
That TypeScript, the tool,also adds a transpiler is a distraction that made a lot of people believe TS is a different language. But the TS folks have always taken great pain to only ever support features that are or are about to be in the ECMAScript standard, and not to deviate from it. That they did initially with some namespace stuff and enums was before ES2015, when JS was lacking some things many people thought were essential. Even then they only added less than a handful of "TypeScript-code".
When you look at the Babel "transpiler" for Typescript, before they added a bit more for class stuff, it pretty much showed that "transpilation" of TS to JS - as long as you targeted a recent ES version - was achieved by doing nothing more than to remove all those type annotations.
I'm still mad at the TS guiys for muddying the waters so much by confusing soooo many people by bundling type checking and transpilation in one tool. This could have been much more clear. I too stuck to using Flow for quite some time until I realized TypeScript really is Javascript, while Flow communicated in its architecture and usage already that it just "added types" (literally).
That's another language. Javascript doesn't have type annotations - even the suggested addition of type annotation syntax to JS[0] doesn't actually do anything because it can't and still be Javascript. Javascript doesn't have enums. Javascript doesn't have interfaces. That 1% (although it's probably more than that) matters. If it can't run, unaltered, in a Javascript interpreter it isn't Javascript.