theptrk/app.js

## app.js
// js goes here
console.log("hello js")

## index.html
<!DOCTYPE html>
<html>
<head>
    <title>Your Website</title>
    <link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>
  <h1>Hello html</h1>
  <script src='app.js'></script>
</body>
</html>

## styles.css
html {
    font-size:2em;
}
	<!DOCTYPE html>
	<html>
	<head>
	<title>Your Website</title>
	<link rel="stylesheet" type="text/css" href="styles.css">
	</head>
	<body>
	<h1>Hello html</h1>
	<script src='app.js'></script>
	</body>
	</html>