content1

content2

原理: ResizeObserver

                        const resizeObserver = new ResizeObserver(entries => {
                            for (let entry of entries) {
                               
                                console.log(entry.target.id, `height:${entry.contentRect.height}  width:${entry.contentRect.width}`);
                            }
                        });
                        resizeObserver.observe(document.querySelector('#my_element'));
                        resizeObserver.observe(document.querySelector('#my_element2'));