TypeScript methods for color conversion

Colors.ts

export type HSL = [number, number, number]

export function HexToHSL(hex: string): HSL | undefined {
  const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex)
  if (!result) return undefined

  const r = parseInt(result[1], 16) / 255
  const g = parseInt(result[2], 16) / 255
  const b = parseInt(result[3], 16) / 255
  const max = Math.max(r, g, b)
  const min = Math.min(r, g, b)

  const l = (max + min) / 2
  if (max === min) return [0, 0, l] // achromatic

  const d = max - min
  const s = l > 0.5 ? d / (2 - max - min) : d / (max + min)

  let h
  if (max === r) h = (g - b) / d + (g < b ? 6 : 0)
  else if (max === g) h = (b - r) / d + 2
  else h = (r - g) / d + 4
  h /= 6

  return [h, s, l]
}

export function HSLToString(hsl: HSL): string {
  let [h, s, l] = hsl
  h = Math.round(h * 360)
  s = Math.round(s * 100)
  l = Math.round(l * 100)
  return `hsl(${h}, ${s}%, ${l}%)`
}