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printPostSubmitMessage
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【問題点】
この機能は「右クリック→フレームを再読み込み」を行うと、FormをSubmit指定なくても、
Submitしたと認識する誤動作が発生する。
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	function printPostSubmitMessage(el_control,html){
		el_control.addEventListener("destroy-gframe",function(e){
			const detail=e.detail;
			const loadidx=detail.loadidx;
			if(loadidx>=2){
				const el=document.createElement("div");
				el.innerHTML=html;
				el_control.after(el.firstElementChild);
				el_control.remove();
			}
		});
	};
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[ How to call 'printPostSubmitMessage' ]
	printPostSubmitMessage(el_control,String.raw`
<div class="knquiz knquiz-reset" style="margin:10px;padding:10px;border:1px solid #faa;color:black;background-color:#fcc;font-size:32px;font-style:italic;">
Thank you for submitting your answer!!!
</div>
	`);
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