html
<iframe id="myIframe" frameborder="0" width="100%" scrolling="no" onload="this.height = this.contentWindow.document.body.scrollHeight+300">
</iframe>
javascript
$('#myIframe').load(function () {
//body{text-align:center;}
// table{margin:0px auto;}
$('#myIframe').contents().find("head").append($(`<style>
ol{
list-style:none !important;
list-style-type:none !important;
}
ul{
list-style:none !important;
list-style-type:none !important;
}
table{border-top:1px solid #7F7F7F!important;border-left:1px solid #7F7F7F!important;border-collapse:collapse;}
table td{
border-bottom:1px solid #7F7F7F!important;border-right:1px solid #7F7F7F!important;padding:5px 12px;
word-break:break-all !important;word-wrap:break-word !important;
vertical-align:middle !important;text-align:center !important;
}
</style>`));
$('#myIframe').contents().find("head").append($(`<link rel="stylesheet" type="text/css" href="static/Ueditor/third-party/SyntaxHighlighter/shCoreDefault.css"/>`));
var script = document.createElement("script");
script.type = "text/javascript";
script.charset = "utf-8";
script.text = `
const pre = document.getElementsByTagName('pre');
for(let me of pre){
me.setAttribute("class","syntaxhighlighter");
}
`;
$('#myIframe').contents().find("head").get(0).appendChild(script);
setTimeout(function(){//一定要加延时,不然有问题
$('#myIframe').get(0).height = $('#myIframe').get(0).contentWindow.document.body.scrollHeight+300;//多加点
}, 100);
});