Javascript: HEX to RGB to HSL

hex2hsl.js

function hexToHSL(hex) {
  var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    r = parseInt(result[1], 16);
    g = parseInt(result[2], 16);
    b = parseInt(result[3], 16);
    r /= 255, g /= 255, b /= 255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h, s, l = (max + min) / 2;
    if(max == min){
      h = s = 0; // achromatic
    }else{
      var d = max - min;
      s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
      switch(max){
        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
        case g: h = (b - r) / d + 2; break;
        case b: h = (r - g) / d + 4; break;
      }
      h /= 6;
    }
  var HSL = new Object();
  HSL['h']=h;
  HSL['s']=s;
  HSL['l']=l;
  return HSL;
}

Thank you! Here is a variation that returns in hsl() CSS format, e.g. hexToCssHsl(#1d4e8f) ➡️ hsl(214,66%,34%):

function hexToCssHsl(hex, valuesOnly = false) {
  var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
  var r = parseInt(result[1], 16);
  var g = parseInt(result[2], 16);
  var b = parseInt(result[3], 16);
  var cssString = '';
  r /= 255, g /= 255, b /= 255;
  var max = Math.max(r, g, b), min = Math.min(r, g, b);
  var h, s, l = (max + min) / 2;
  if (max == min) {
    h = s = 0; // achromatic
  } else {
    var d = max - min;
    s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
    switch(max) {
      case r: h = (g - b) / d + (g < b ? 6 : 0); break;
      case g: h = (b - r) / d + 2; break;
      case b: h = (r - g) / d + 4; break;
    }
    h /= 6;
  }
  
  h = Math.round(h * 360);
  s = Math.round(s * 100);
  l = Math.round(l * 100);
  
  cssString = h + ',' + s + '%,' + l + '%';
  cssString = !valuesOnly ? 'hsl(' + cssString + ')' : cssString;
  
  return cssString;
}

Btw, I never knew about the /= division assignment operator until today 🤯

Awesome job! Thank you!

Typescript version that avoids var and ==:

function hexToCssHsl(hex: string, valuesOnly = false) {
    const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    if (!result || result.length !== 3) throw "Failed to parse hex";

    let r = parseInt(result[1], 16);
    let g = parseInt(result[2], 16);
    let b = parseInt(result[3], 16);
    let cssString = "";
    (r /= 255), (g /= 255), (b /= 255);
    const max = Math.max(r, g, b),
        min = Math.min(r, g, b);
    let h,
        s,
        l = (max + min) / 2;
    if (max === min) {
        h = s = 0; // achromatic
    } else {
        const d = max - min;
        s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
        switch (max) {
            case r:
                h = (g - b) / d + (g < b ? 6 : 0);
                break;
            case g:
                h = (b - r) / d + 2;
                break;
            case b:
                h = (r - g) / d + 4;
                break;
        }
        h /= 6;
    }

    h = Math.round(h * 360);
    s = Math.round(s * 100);
    l = Math.round(l * 100);

    cssString = h + "," + s + "%," + l + "%";
    cssString = !valuesOnly ? "hsl(" + cssString + ")" : cssString;

    return cssString;
}