iframe不显示滚动条并且设置动态高度、添加内部样式和脚本

<iframe id="myIframe" frameborder="0" width="100%" scrolling="no" onload="this.height = this.contentWindow.document.body.scrollHeight+300">
iframe>

$('#myIframe').load(function () {
				//body{text-align:center;}
				// table{margin:0px auto;}
				$('#myIframe').contents().find("head").append($(``));
				$('#myIframe').contents().find("head").append($(``));

				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);
			});