Pen Settings



CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource


Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource


Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.


Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.


                <div id="page-wrapper">
  <h1>requestAnimationFrame Demo</h1>

  <div class="controls">
    <button type="button" id="startBtn">Start Animation</button>
    <button type="button" id="stopBtn">Stop Animation</button>
    <button type="button" id="resetBtn">Reset</button>

  <canvas id="stage" width="640" height="100"></canvas>


                html {
  font-family: Helvetica, Arial, sans-serif;
  font-size: 100%;
  background: #333;

#page-wrapper {
  width: 640px;
  background: #FFFFFF;
  padding: 1em;
  margin: 1em auto;
  border-top: 5px solid #69c773;
  box-shadow: 0 2px 10px rgba(0,0,0,0.8);

h1 {
  margin-top: 0;

canvas {
  background: #EEE;

.controls {
  margin: 1em 0;

button {
  display: inline-block;
  border-radius: 3px;
  border: none;
  font-size: 0.9rem;
  padding: 0.4rem 0.8em;
  background: #69c773;
  border-bottom: 1px solid #498b50;
  color: white;
  -webkit-font-smoothing: antialiased;
  font-weight: bold;
  margin: 0 0.25rem;
  text-align: center;

button:hover, button:focus {
  opacity: 0.75;
  cursor: pointer;

button:active {
  opacity: 1;
  box-shadow: 0 -3px 10px rgba(0, 0, 0, 0.1) inset;



// requestAnimationFrame polyfill by Erik Möller. fixes from Paul Irish and Tino Zijdel
// MIT license
(function() {
    var lastTime = 0;
    var vendors = ['ms', 'moz', 'webkit', 'o'];
    for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
        window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
        window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] 
                                   || window[vendors[x]+'CancelRequestAnimationFrame'];
    if (!window.requestAnimationFrame)
        window.requestAnimationFrame = function(callback, element) {
            var currTime = new Date().getTime();
            var timeToCall = Math.max(0, 16 - (currTime - lastTime));
            var id = window.setTimeout(function() { callback(currTime + timeToCall); }, 
            lastTime = currTime + timeToCall;
            return id;
    if (!window.cancelAnimationFrame)
        window.cancelAnimationFrame = function(id) {

(function() {

	// Get the buttons.
	var startBtn = document.getElementById('startBtn');
	var stopBtn = document.getElementById('stopBtn');
	var resetBtn = document.getElementById('resetBtn');

	// A variable to store the requestID.
	var requestID;

	// Canvas
	var canvas = document.getElementById('stage');

	// 2d Drawing Context.
	var ctx = canvas.getContext('2d');

	// Set the fill style for the drawing context.
	ctx.fillStyle = '#212121';

	// Variables to for the drawing position and object.
	var posX = 0;
	var boxWidth = 50;
	var pixelsPerFrame = 5; // How many pixels the box should move per frame.

	// Draw the initial box on the canvas.
	ctx.fillRect(posX, 0, boxWidth, canvas.height);

	// Animate.
	function animate() {
		requestID = requestAnimationFrame(animate);

		// If the box has not reached the end draw on the canvas.
		// Otherwise stop the animation.
		if (posX <= (canvas.width - boxWidth)) {
			ctx.clearRect((posX - pixelsPerFrame), 0, boxWidth, canvas.height);
			ctx.fillRect(posX, 0, boxWidth, canvas.height);
			posX += pixelsPerFrame;
		} else {

	// Event listener for the start button.
	startBtn.addEventListener('click', function(e) {

		// Start the animation.
		requestID = requestAnimationFrame(animate);

	// Event listener for the stop button.
	stopBtn.addEventListener('click', function(e) {

		// Stop the animation;

	// Event listener for the reset button.
	resetBtn.addEventListener('click', function(e) {

		// Reset the X position to 0.
		posX = 0;

		// Clear the canvas.
		ctx.clearRect(0, 0, canvas.width, canvas.height);

		// Draw the initial box on the canvas.
		ctx.fillRect(posX, 0, boxWidth, canvas.height);