004.ResizeObserver

// 创建观察器实例
const resizeObserver = new ResizeObserver(entries => {
  for (const entry of entries) {
    const { height } = entry.contentRect;
    console.log('元素高度变化:', height);
  }
});
 
// 开始观察目标元素
const targetElement = document.getElementById('target');
resizeObserver.observe(targetElement);
 
// 停止观察
function stopObserving() {
  resizeObserver.unobserve(targetElement);
  // 或彻底断开所有观察：resizeObserver.disconnect();
}