[maxxxxx]

With all the dynamic stuff Javascript has it seems really difficult to create performant C code.

There is a PHP to .NET compiler which probably has similar problems. On second thought that one is probably easier because .NEt has a dynamic runtime.

[nicoburns]

That, and in practice modern PHP is often relatively staticly typed (classes declare their fields, etc), and many codebases even include type annotations (which are supported in PHP and usually enforced at runtime).