Lighten and Darken Color

function lightenDarkenColor(color, amt, isDarken) {
  let col = color;
  let usePound = false;
  const diff = isDarken ? ~amt + 1 : amt;

  if (col[0] === '#') {
    col = col.slice(1);
    usePound = true;
  }

  const num = parseInt(col, 16);

  let r = (num >> 16) + diff;

  if (r > 255) r = 255;
  else if (r < 0) r = 0;

  let b = ((num >> 8) & 0x00ff) + diff;

  if (b > 255) b = 255;
  else if (b < 0) b = 0;

  let g = (num & 0x0000ff) + diff;

  if (g > 255) g = 255;
  else if (g < 0) g = 0;

  return (usePound ? '#' : '') + (g | (b << 8) | (r << 16)).toString(16);
}

export const darken = (color, amt) => lightenDarkenColor(color, amt, true);

export const lighten = (color, amt) => lightenDarkenColor(color, amt);