手写滚动条滚动动画

 /**
     * 滚动动画
     * @param {HTMLElenent} divDode -滚动条dom
     * @param {number} position - 距离
     * @param {'x'|'y'} direction - 滚动方向
     * @param {number} time - 动画时间
     */
    scrollAnimation(divDode, position, direction, time, fps) {
      clearInterval(this.scrollManTimer);
      divDode = divDode || window;
      fps = fps || 16;
      time = time || 300;
      direction = direction || 'y';
      let attr = direction === 'x' ? 'pageXOffset' : 'pageYOffset';
      let attr2 = direction === 'x' ? 'scrollLeft' : 'scrollTop';
      let scrollLength = divDode[attr] || divDode[attr2];
      let count = 0;
      let totalCount = Math.floor(time / fps);
      let slice = (position - scrollLength) / totalCount;
      this.scrollManTimer = setInterval(() => {
        this.scroll(divDode, direction, slice);
        count++;
        if (count === totalCount) {
          clearInterval(this.scrollManTimer);
          let length = position - divDode[attr];
          if (length === 0) return;
          setTimeout(() => {
            this.scroll(divDode, direction, length);
          }, fps);
        }
      }, fps);
    },
 scroll(divDode, direction, number) {
      divDode = divDode || window;
      let x = direction === 'x' ? number : 0;
      let y = direction === 'y' ? number : 0;
      divDode.scrollBy(x, y);
    },