It's too ad-hoc and over-complicated to implement common things such as classes and interfaces. In JavaScript you're essentially stuck with stringly typed value

It's too ad-hoc and over-complicated to implement common things such as classes and interfaces. In JavaScript you're essentially stuck with stringly typed values and chaining mix-ins together to emulate a class hierarchy. It's also difficult to get instanceof to work as one would expect. The other languages I'm used to all natively support it: Python and Java. Granted, Java is single-inheritance too but you can implement multiple interfaces.