Is it? I thought Javascript has integer type.

Say for example Lua (by default) is configured to use only double. It can be configured to use single-float, or even integer - but only one numeric type.

Standard JavaScript uses doubles everywhere. They get casted to 32-bit signed integers for bitwise operations, the results are casted back. It's a little odd, but consistent at least.

A little odd and a lot slow, if you do them a lot (js-protobuf, I'm looking at you).

Execution tracing should eliminate the cast if it is not necessary.

Ah. I don't know the inner workings of Javascript so I'm not surprised I was wrong. Just at a glance, that problem to me screams floating point limitation.