resize iframe listener

resizeIframe

// child.html
  let height;
  const sendPostMessage = () => {
    if (height !== document.getElementById('container').offsetHeight) {
      height = document.getElementById('container').offsetHeight;
      window.parent.postMessage({
        frameHeight: height
      }, '*');
      console.log(height);
    }
  }
  window.onload = () => sendPostMessage();
  window.onresize = () => sendPostMessage();
  document.getElementById('add-para').onclick = () => sendPostMessage();
  document.getElementById('remove-para').onclick = () => sendPostMessage();
// parent.html
<iframe id="i" src="child.html" style="width:100%;border:none;"></iframe><script>window.onmessage=e=>{e.data.hasOwnProperty("frameHeight")&&(document.getElementById("i").style.height=`${e.data.frameHeight+30}px`)}</script>