One caveat not mentioned is that while float is 64 bit floating point number, int is only 53 bit integer, unlike having 64 bit int in most other languages. Yeah, I've got bitten by this before causing a nasty bug.
There is no "int" or "float" (mostly[1]) — there is only Number, which is an IEEE floating point. A literal `1` is a floating point that happens to be precisely representing an integer. "53 bits" happens to be the limit of consecutive integers that you can store in an IEEE double.
[1]: 32-bit integers show up under the hood, in expressions such as `5000000000|0`. Both 0 and 5000000000 are precisely represented in JS's Number type, but you cannot (correctly) take a binary OR of the two.
The biggest gotchas with whole numbers in JS (IEE754 64-bit floats) is that in JS all bitwise operations are performed on a 32-bit integer under the hood... in practice this means you can do a bitwise operation on anything and it will be coerced into a 32-bit integer, either first via the parseInt(X,10) path, or becomes an empty 0 value.
It really isn't unique to JS, and there are several bignum libraries that can/will help.
