Haxe is multi-targeted. It compiles to PHP, C++, Neko Bytecode, etc. Being a high-level language, and using the same compiler infrastructure, it would have to

Haxe is multi-targeted. It compiles to PHP, C++, Neko Bytecode, etc. Being a high-level language, and using the same compiler infrastructure, it would have to be transpiled into a fairly low-level IR for the consumption of the various backends before being spit out as JS again. I think the fact that its high level makes it much LESS simple. It definitely isn't just mapping Haxe constructs to JS. It is much too feature rich.