All numbers in Javascript are IEEE 754 64-bit double precision floating point numbers. The significand precision is 53 bits (see here https://en.wikipedia.org/wiki/Double-precision_floating-poin...).

Thanks for the clarifications.

Re ctypes, I assume you are talking about https://developer.mozilla.org/en-US/docs/Mozilla/js-ctypes. On that page you can read:

> js-ctypes is only available from chrome code; that is, ctypes is not available to websites, only application and extension code.

Basically `js-ctypes` won't work in an actual browser. So you cannot use it. There are other Node.js-specific native packages that give a representation for 64-bit integers, but not arithmetic operations. Besides, even if they had arithmetic operations, they would be heap-allocated, and since the JIT cannot understand them, it would not be able to optimize them as well as what we built for Scala.js.