A TypeScript implementation of the `mround` function from Google Sheets, Microsoft Excel etc.

mround.ts

/**
 * Rounds one number to the nearest integer multiple of another.
 * @param value The number to round to the nearest integer multiple of another.
 * @param factor The number to whose multiples value will be rounded.
 * @example 
 * mround(10, 3); // 9
 * mround(-10, -3); // -9
 * mround(5, -2); // Error: Parameters of mround must have same signs (both positive or both negative)
 */
export function mround(value: number, factor: number): number {
  if (Math.abs(value) === 0 || Math.abs(factor) === 0) {
    return 0;
  }
  if (Math.sign(value) !== Math.sign(factor)) {
    throw new Error('Parameters of mround must have same signs (both positive or both negative).');
  }
  return Math.round(value / factor) * factor;
}