function hexify(color) {
    var values = color
      .replace(/rgba?\(/, '')
      .replace(/\)/, '')
      .replace(/[\s+]/g, '')
      .split(',');
    var a = parseFloat(values[3] || 1),
        r = Math.floor(a * parseInt(values[0]) + (1 - a) * 255),
        g = Math.floor(a * parseInt(values[1]) + (1 - a) * 255),
        b = Math.floor(a * parseInt(values[2]) + (1 - a) * 255);
    return "#" +
      ("0" + r.toString(16)).slice(-2) +
      ("0" + g.toString(16)).slice(-2) +
      ("0" + b.toString(16)).slice(-2);
  }
  console.log(hexify('rgba(0, 0, 0, 0.05)'))