'you don't have to consider things like undefined, null, NaN, negative numbers, strings and so on.'

But as the Math object has been reset you shouldnt use Math.floor in the first method Math.round

.

This does not work correctly for negative numbers.

Standard Math object: Math.floor(-1.1) === -2

This implementation: Math.floor(-1.1) === -1

Great idea reusing functions

Hmm... almost the same...

I guess mine is slightly better since % works for bigger numbers...