Javascript IEEE 754 floating-point remainder of x / y

remainder.ts

/** Computes the IEEE 754 floating-point remainder of x / y. */
export const remainder = (x: number, y: number): number => {
  if (isNaN(x) || isNaN(y) || !isFinite(x) || y === 0) return NaN

  const quotient = x / y
  let n = Math.round(quotient)

  // When quotient is exactly halfway between two integers, round to the nearest even integer
  if (Math.abs(quotient - n) === 0.5) n = 2 * Math.round(quotient / 2)

  const rem = x - n * y
  return !rem ? Math.sign(x) * 0 : rem
}