Round orders of magnitude in JS.

m.js

function m(n, d) {
  P = Math.pow;
  R = Math.round
  d = P(10, d);
  i = 7;

 while(i) {
   (s = P(10, i-- * 3)) <= n && (n = R(n * d / s) / d + "KMGTPE"[i])
  }

  return n;
}