Javascript - round number to N decimal places

round_number_to_decimals.js

/*
NOTES:
   not totally exact. if you need consistent rounding on a high degree - search further
   see also: https://stackoverflow.com/questions/11832914/how-to-round-to-at-most-2-decimal-places-if-necessary
*/

const DECIMAL_MUL = {
  1: 10,
  2: 100,
  3: 1000,
  4: 10000,
  5: 100000,
}

function RoundToDecimals(dec, num) {
  let mul = DECIMAL_MUL[dec];
  return Math.round((num + Number.EPSILON) * mul) / mul;
}

RoundToDecimals(2, 2.49884444)  # 2.49
RoundToDecimals(4, 98.349237482)  # 98.3492