You can still use Math.floor, and simply shift the answer by an order of magnitude:
const moreFloor = n => Math.floor (n / 10) * 10 || n;
// (or if you prefer...)
function moreFloor (n) {
return Math.floor (n / 10) * 10 || n;
}
Just to clarify, the || n
at the end of the expression is due to the particular requirement in the question to not round down any number less than ten. If readers want moreFloor(9) === 0
, you can omit that part.
solved Javascript round down whole number