親フォルダ タブ 
<!DOCTYPE html>
<html>
<head>
<meta content="width=device-width initial-scale=1.0 minimum-scale=1.0 maximum-scale=1.0 user-scalable=no" name="viewport">
<meta charset="UTF-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.1/css/bootstrap.css">
<style>
pre {
	padding: 20px;
}
</style>
<script>
function test1() {
	var wareki = ["明治", "大正", "昭和", "平成", "令和"];

	var text = "";

	$.each(wareki, function( key, value ){
		text += key + " => " + value + "\n";
	});

	document.getElementById("text1").innerText = text;
}

function test2() {
	var wareki = ["明治", "大正", "昭和", "平成", "令和"];

	var text = "";

	$(wareki).each(function( index ){
		text += index + " => " + this + "\n";
	});

	document.getElementById("text2").innerText = text;
}

</script>
</head>
<body>

<div>
	<input type="button" value="実行1" onclick="test1()">
	<input type="button" value="実行2" onclick="test2()">
</div>

<pre id="text1">
</pre>
<pre id="text2">
</pre>

</body>
</html>