cssAudio - Activefile-genericCSS - ActiveGeneric - ActiveHTML - ActiveImage - ActiveJS - ActiveSVG - ActiveText - Activefile-genericVideo - ActiveLovehtmlicon-new-collectionicon-personicon-teamlog-outoctocatpop-outspinnerstartv

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

You're using npm packages, so we've auto-selected Babel for you here, which we require to process imports and make it all work. If you need to use a different JavaScript preprocessor, remove the packages in the npm tab.

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

Use npm Packages

We can make npm packages available for you to use in your JavaScript. We use webpack to prepare them and make them available to import. We'll also process your JavaScript with Babel.

⚠️ This feature can only be used by logged in users.

Code Indentation

     

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.

            
              <h2>Understanding JSX</h2>

<p>
	This is an HTML page with a single babel-transpiled JS file and no dependencies.
	It is rendering DOM via JSX without any frameworks.
</p>
            
          
!
            
              body {
	padding: 20px 20px 320px;
}
* {
	box-sizing: border-box;
}
pre {
	position: absolute;
	bottom: 0;
	left: 0;
	width: 100%;
	max-height: 300px;
	padding: 10px;
	margin: 0;
	background: #F3F3F3;
	border-top: 1px solid #CCC;
	box-shadow: inset 0 1px 10px rgba(0,0,0,0.2);
	font: 11px/1.1 Menlo,Monaco,'Courier New',courier;
	color: #555;
	overflow: auto;
}
            
          
!
            
              /** @jsx h */

// ^^^^ this tells a transpiler to inject calls to an `h()` function for each node.

const ITEMS = 'hello there people'.split(' ');

// a "partial" that does a filtered loop - no template BS, just functional programming:
function foo(items) {
	// imagine templates that adhere to your JS styleguide...
	return items.map( p => <li> {p} </li> );		// <-- can be multiline
}

// a simple JSX "view" with a call out ("partial") to generate a list from an Array:
let vdom = (
	<div id="foo">
		<p>Look, a simple JSX DOM renderer!</p>
		<ul>{ foo(ITEMS) }</ul>
	</div>
);

// render() converts our "virtual DOM" (see below) to a real DOM tree:
let dom = render(vdom);

// append the new nodes somewhere:
document.body.appendChild(dom);

// Remember that "virtual DOM"? It's just JSON - each "VNode" is an object with 3 properties.
let json = JSON.stringify(vdom, null, '  ');

// The whole process (JSX -> VDOM -> DOM) in one step:
document.body.appendChild(
	render( <pre>{ json }</pre> )
);





/** Render Virtual DOM to the real DOM */
function render(vnode) {
	if (typeof vnode==='string') return document.createTextNode(vnode);
	let n = document.createElement(vnode.nodeName);
	Object.keys(vnode.attributes || {}).forEach( k => n.setAttribute(k, vnode.attributes[k]) );
	(vnode.children || []).forEach( c => n.appendChild(render(c)) );
	return n;
}

/** hyperscript generator, gets called by transpiled JSX */
function h(nodeName, attributes, ...args) {
	let children = args.length ? [].concat(...args) : null;
	return { nodeName, attributes, children };
}


/*
// here's an alternative hyperscript-to-vdom method that creates sparse nodes:
function h(nodeName, attributes, ...args) {
	let vnode = { nodeName };
	if (attributes) vnode.attributes = attributes;
	if (args.length) vnode.children = [].concat(...args);
	return vnode;
}
*/

            
          
!
999px
🕑 One or more of the npm packages you are using needs to be built. You're the first person to ever need it! We're building it right now and your preview will start updating again when it's ready.
Loading ..................

Console