<!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">
<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 = "";
for( var i = 0; i < wareki.length; i++ ) {
text += i + " => " + wareki[i] + "\n";
}
document.getElementById("text1").innerText = text;
}
function test2() {
var wareki = ["明治", "大正", "昭和", "平成", "令和"];
var text = "";
wareki.forEach( function(value, i){
text += i + " => " + value + "\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>