Javascript - Generate random dark color

Question

I have this method to generate me random colors for font:

function getRandomRolor() {
     var letters = '0123456789ABCDEF'.split('');
     var color = '#';
     for (var i = 0; i < 6; i++) {
         color += letters[Math.round(Math.random() * 15)];
     }
     return color;
}  

The problem is that the font is always on white background, I want to generate dark colors.
Is it possible?
Thanks

Answer 1

You could use a custom function that takes a hex and darkens it by the percent lum. You can modify it to return whatever you want back

function ColorLuminance(hex, lum) {
  // validate hex string
  hex = String(hex).replace(/[^0-9a-f]/gi, '');
  if (hex.length < 6) {
    hex = hex[0]+hex[0]+hex[1]+hex[1]+hex[2]+hex[2];
  }
  lum = lum || 0;

  // convert to decimal and change luminosity
  var rgb = "#", c, i;
  for (i = 0; i < 3; i++) {
    c = parseInt(hex.substr(i*2,2), 16);
    c = Math.round(Math.min(Math.max(0, c + (c * lum)), 255)).toString(16);
    rgb += ("00"+c).substr(c.length);
  }

  return rgb;
}

You could also just use hsl (Hugh, Saturation, Luminosity or Lightness). The hsl link actually goes through the above code.

Answer 2

As you know RGB at 0,0,0 is black the darkest and it goes toward getting light until (255,255,255) so you can stop it to go above 100, to get only dark colors or say 9 in hex:

Here is jsFiddle

function getDarkColor() {
    var color = '#';
    for (var i = 0; i < 6; i++) {
        color += Math.floor(Math.random() * 10);
    }
    return color;
}