Note that the data type sizes don’t need to match, so it’s no problem to have a union with, for example, a 32-bit and a single 8-bit integer, the 8-bit value is simply truncated if needed.

Unlike many other languages, JavaScript does not distinguish between integers and floating-point numbers. 42 and 3.14 are both Number types. BigInt, as its name suggests, only covers integers, and ...