if лишний
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
*{
text-align: center;
}
</style>
</head>
<body>
<script>
function fn(a) {
0 < a && fn(a - 1);
for (var b = 1; a; b += 2) {
--a; document.write("*".repeat(b) + "<br>");
}
}
fn(5)
</script>
</body>
</html>