hex alpha

color.ts

export const alpha = (color: string, opacity: number) => {
  // if it has an alpha, remove it
  if (color.length > 7) {
    color = color.substring(0, color.length - 2);
  }

  // coerce values so ti is between 0 and 1.
  const newOpacity = Math.round(Math.min(Math.max(opacity, 0), 1) * 255);
  let opacityHex = newOpacity.toString(16).toUpperCase();

  // opacities near 0 need a trailing 0
  if (opacityHex.length === 1) {
    opacityHex = `0${opacityHex}`;
  }

  return color + opacityHex;
};