如何使iFrame高度自适应？

<script type="text/javascript">
    function resizeIframe() {
        var iframe = document.getElementById('myiframe');
        iframe.style.height = iframe.contentWindow.document.body.scrollHeight + 'px';
    }
</script>

<iframe id="myiframe" src="http://www.example.com" onload="resizeIframe()"></iframe>

<iframe src="http://www.example.com" style="height: 100%"></iframe>

<script type="text/javascript">
    var observer = new MutationObserver(function(mutations) {
        var iframe = document.getElementById('myiframe');
        iframe.style.height = iframe.contentWindow.document.body.scrollHeight + 'px';
    });
    
    var config = { attributes: true, childList: true, characterData: true };
    var target = document.getElementById('myiframe').contentDocument.body;
    
    observer.observe(target, config);
</script>

<iframe id="myiframe" src="http://www.example.com"></iframe>