以编程方式使十六进制颜色变暗

function darkenHexColor(hexColor, amount) {
  const num = parseInt(hexColor.slice(1), 16);
  const r = (num >> 16) + amount;
  const b = ((num >> 8) & 0x00ff) + amount;
  const g = (num & 0x0000ff) + amount;
  const newColor = (
    (r < 255 ? r < 1 ? 0 : r : 255) * 0x10000 +
    (b < 255 ? b < 1 ? 0 : b : 255) * 0x100 +
    (g < 255 ? g < 1 ? 0 : g : 255)
  ).toString(16);
  return "#" + (newColor.length === 5 ? "0" : "") + newColor;
}

const hexColor = "#FF5733";
const amount = -100;
const darkerHexColor = darkenHexColor(hexColor, amount);
console.log(darkerHexColor); // 输出 "#BF3D1F"