getContrast color function

getContrast

var getContrast = function(background, foreground) {

  // Convert hex to rgb
  var backgroundRGB = 'rgb(' + (background = background.replace('#', '')).match(new RegExp('(.{' + background.length/3 + '})', 'g')).map(function(l) { return parseInt(background.length%2 ? l+l : l, 16); }).join(',') + ')';

  var foregroundRGB = 'rgb(' + (foreground = foreground.replace('#', '')).match(new RegExp('(.{' + foreground.length/3 + '})', 'g')).map(function(l) { return parseInt(foreground.length%2 ? l+l : l, 16); }).join(',') + ')';

  // Get array of RGB values
  var backgroundRGBArray = backgroundRGB.replace(/[^\d,]/g, '').split(',');
  var foregroundRGBArray = foregroundRGB.replace(/[^\d,]/g, '').split(',');

  function luminance(r, g, b) {
      var a = [r, g, b].map(function (v) {
          v /= 255;
          return v <= 0.03928 ? v / 12.92 : Math.pow( (v + 0.055) / 1.055, 2.4 );
      });
      return a[0] * 0.2126 + a[1] * 0.7152 + a[2] * 0.0722;
  }

  function floor(number, decimals) {
    decimals = +decimals || 0;

    var multiplier = Math.pow(10, decimals);

    return Math.floor(number * multiplier) / multiplier;
}

  function contrast(el1, el2) {
    l1 = (luminance(el1[0], el1[1], el1[2]) + 0.05);
    l2 =(luminance(el2[0], el2[1], el2[2]) + 0.05);
    ratio = l1/l2;

    if (l2 > l1) {
      ratio = 1 / ratio;
    } 
    
    return floor(ratio, 2);
  }
  
  var contrast = contrast(backgroundRGBArray, foregroundRGBArray);
  return contrast;
}