h2sl.js

const h2sl = (hex, isString) => {
  // Convert hex to RGB first
  let r = 0, g = 0, b = 0
  
  if (hex.length == 4) {
    r = "0x" + hex[1] + hex[1]
    g = "0x" + hex[2] + hex[2]
    b = "0x" + hex[3] + hex[3]
  } else if (hex.length == 7) {
    r = "0x" + hex[1] + hex[2]
    g = "0x" + hex[3] + hex[4]
    b = "0x" + hex[5] + hex[6]
  }
  
  // Then to HSL
  r /= 255
  g /= 255
  b /= 255
  
  let cmin = Math.min(r,g,b),
      cmax = Math.max(r,g,b),
      delta = cmax - cmin,
      h = 0,
      s = 0,
      l = 0

  if (delta == 0) {
    h = 0
  } else if (cmax == r) {
    h = ((g - b) / delta) % 6
  } else if (cmax == g) {
    h = (b - r) / delta + 2
  } else {
    h = (r - g) / delta + 4
  }
  
  h = Math.round(h * 60)

  if (h < 0) {
    h += 360
  }

  l = (cmax + cmin) / 2
  s = delta == 0 ? 0 : delta / (1 - Math.abs(2 * l - 1))
  s = +(s * 100).toFixed(1)
  l = +(l * 100).toFixed(1)
  
  if(isString) {
    return "hsl(" + h + "," + s + "%," + l + "%)"
  } else {
    return { h, s, l }
  }
}