code: function rgb2hex(rgb) {
        if (/^#[0-9A-F]{6}$/i.test(rgb)) {
          return rgb;
        }
  
        rgb = rgb.match(/^rgb\((\d+),\s*(\d+),\s*(\d+)\)$/);
  
        if (rgb === null) {
          return 'N/A';
        }
  
        function hex(x) {
          return ('0' + parseInt(x).toString(16)).slice(-2);
        }
  
        return '#' + hex(rgb[1]) + hex(rgb[2]) + hex(rgb[3]);
      }
docs: convert rgb to hex value string