JavaScript动画中如何用贝塞尔曲线实现数字的平滑增长？

// 贝塞尔曲线控制点和参数
const startx = 0;
const starty = 0;
const cp1x = 0.1;
const cp1y = 0.4;
const cp2x = 0.1;
const cp2y = 1;
const endx = 1;
const endy = 1;

// 计算贝塞尔曲线在t时刻的y坐标
function bezier(t) {
  const cx = 3 * (cp1x - startx);
  const cy = 3 * (cp1y - starty);
  const bx = 3 * (cp2x - cp1x) - cx;
  const by = 3 * (cp2y - cp1y) - cy;
  const ax = endx - startx - cx - bx;
  const ay = endy - starty - cy - by;
  const x = ax * t * t * t + bx * t * t + cx * t + startx;
  const y = ay * t * t * t + by * t * t + cy * t + starty;
  return y;
}

// 模拟数字增长，贝塞尔曲线控制速度
let count = 0;
const target = 1000;
const duration = 3000; // 动画持续时间 (毫秒)
const startTime = Date.now();

function update() {
  const elapsed = Date.now() - startTime;
  const t = Math.min(1, elapsed / duration); // 确保t在0-1之间
  count = Math.round(bezier(t) * target);
  if (elapsed < duration) {
    requestAnimationFrame(update);
  }
  render();
}

function render() {
  document.getElementById('count').textContent = count; // 将数字显示在id为'count'的元素中
}

update();