index.htm.
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF8">
<title>JavaScriptの勉強</title>
</head>
<body>
<h1>JavaScriptの勉強</h1>
<script>
// 条件分岐(if)
var score = 80;
// 比較演算子
// >= <= < >
// == !=
if (score >= 70) {
alert("合格！");
}
</script>
</body>
</html>