/code/javascript/run.html

<!DOCTYPE html>
<html>
<head>
	<title>Text editor</title>
	<style type="text/css">
		html, body, textarea {
			height: 100%;
			width: 100%;
			margin: 0;
			border: 0;
			padding: 0;
		}
	</style>
	<script type="text/javascript">
onload = function () {
	document.querySelector("button").onclick =
		() => eval(document.querySelector("textarea").value);
}
	</script>
</head>
<body><textarea></textarea><button>go</button></body>
</html>
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