Calculate brightness value by RGB or HEX color

brightnessByColor.js

/**
 * Calculate brightness value by RGB or HEX color.
 * @param color (String) The color value in RGB or HEX (for example: #000000 || #000 || rgb(0,0,0) || rgba(0,0,0,0))
 * @returns (Number) The brightness value (dark) 0 ... 255 (light)
 */
function brightnessByColor (color) {
  var color = "" + color, isHEX = color.indexOf("#") == 0, isRGB = color.indexOf("rgb") == 0;
  if (isHEX) {
    var m = color.substr(1).match(color.length == 7 ? /(\S{2})/g : /(\S{1})/g);
    if (m) var r = parseInt(m[0], 16), g = parseInt(m[1], 16), b = parseInt(m[2], 16);
  }
  if (isRGB) {
    var m = color.match(/(\d+){3}/g);
    if (m) var r = m[0], g = m[1], b = m[2];
  }
  if (typeof r != "undefined") return ((r*299)+(g*587)+(b*114))/1000;
}

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This might fix it

/**
 * Calculate brightness value by RGB or HEX color.
 * @param color (String) The color value in RGB or HEX (for example: #000000 || #000 || rgb(0,0,0) || rgba(0,0,0,0))
 * @returns (Number) The brightness value (dark) 0 ... 255 (light)
 */
function brightnessByColor (color) {
  var color = "" + color, isHEX = color.indexOf("#") == 0, isRGB = color.indexOf("rgb") == 0;
  if (isHEX) {
    const hasFullSpec = color.length == 7;
    var m = color.substr(1).match(hasFullSpec ? /(\S{2})/g : /(\S{1})/g);
    if (m) var r = parseInt(m[0] + (hasFullSpec ? '' : m[0]), 16), g = parseInt(m[1] + (hasFullSpec ? '' : m[1]), 16), b = parseInt(m[2] + (hasFullSpec ? '' : m[2]), 16);
  }
  if (isRGB) {
    var m = color.match(/(\d+){3}/g);
    if (m) var r = m[0], g = m[1], b = m[2];
  }
  if (typeof r != "undefined") return ((r*299)+(g*587)+(b*114))/1000;
}