Question

While I understand the Math.round/ceil/floor functions in javascript, I have been unable to come up with a working function to this problem.

What I want to do is round any whole number to a multiple of 3, or in fact any multiple which I choose.

The requirements of the returned numbers when the the multiple value of ‘3’ is given are as follows:

0 returns 0
6 returns 6
7 returns 6
8 returns 9
22 returns 21
23 returns 24

etc..etc… So basically, the returned value will always be a multiple of the given parameter, in this case ‘3’.

Thanks all.

Answer 1

You can use a simple function like this:

function roundMultiple3(num) {
  return(Math.round(num / 3) * 3);
}

This divides by 3, rounds to the nearest integer, then multiplies by 3 again to restore the full value.

Or a generic version that allows you to specify the multiple:

function roundMultiple(num, multiple) {
  return(Math.round(num / multiple) * multiple);
}