underscore.jsを使うとjsがrubyみたいに使えてイケメン

javascript 
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8">
<title>underscore.js test</title>
<script src="underscore.js"></script>
<script>
  var a = _.map([1, 2, 3], function(num){ return num * 3; });
  alert(a);
</script>
</head>
<body>

contents here

</body>
</html>

3,6,9