From tooling's perspective, it is a good practice. While the return type can be inferred, the parameter's could normally be anything which is safe to convert to a number:

multiply("24", true)

Gotta type those arguments.

I just tested this and it seems to be working fine. I would go back and give your code another once over.

Good luck!

Inexplicably breaks for me on random tests. Copied and pasted:
Random Tests
ReferenceError: k is not defined
at Object.Test.describe

Hey, I posted a longer response to another comment in the thread , but it's rounding the number down to an integer.

Rounding the number down to an integer.

~ is the bitwise NOT operator. It flips all the zeros to ones and ones to zeros in a number. But when you do it, JS doesn't use the Floating Point representation of the number, it uses the integere representation. So really ~n means "Instead of a Number, treat n like a string of bits and flip all of those." Then I just do it again to flip it back and I have the integer representation.

For future reference, you can search for symbols on Symbolhound if you see something like this. For instance that's where I learned what :: means in C++ and PHP. It's also where I found this better explanation of ~~ if you want to see another take on this.

Happy coding friend!

Would also be interested to no exactly what's going on here.