View Component Creator : lightweight reactive view components

Usage no npm install needed!

<script type="module">
  import vcc from '';



View Component Creator : lightweight reactive web components
View an Unofficial TodoMVC Todo Application Demo to kick the tires.

View fancier online docs


A light-weight API to create W3 custom elements using a React-like syntax instead of polymer or x-tags. VCC has a one-way data flow into components via attributes, and each component has a private internal state. Built for simplicity (no building, no transpiling, no pre-compilation) on well-tested tools and concepts (registerElement, VDOM, odiff), there are no current plans for major new features, but PRs are welcome.


Use npm install vcc or bower install vcc or just download and include the script file in your page or application. There's no other steps, build processes or large bundles required. With custom html in your document/app and VCC in a script, you're good to go.


HTML Elements

Components expose custom methods and events to non-VCC actors. This makes it easy to set props by changing an attribute, and external props can be hit using CSS2 [attribute] selectors. You can also easily inspect the full properties of the component in devtools without any browser add-ons. Isomorphic apps are easy becuase you just need to generate HTML on the server, which all servers can do (php included). Lastly, serializing the component using ex. elm.outerHTML will define non-default prop values for later use. All we know and love about html, now available in components.

No build process

Changes can be made on the fly to one part without needing to re-bundle the whole application, allowing better caching, on-the-fly patching, and more contextualized error messages. The source of the component is the same code that runs, removing a layer of abstraction while allowing better debugging with simpler tools. More than anything, it's just simpler and more in the spirit of the web where code runs in the open.

Lightweight Runtime

A cat will beat a horse in a race that lasts one second. At about 25kb pre-gzip, VCC doesn't make mobile users wait around to get going. Components arrive in the actual HTML, allowing pre-mounting CSS targeting and accelerated layout. Despite the diminutive size, VCC provides a great API for creating re-usable UI components while embracing web standards.

How it's made

Define custom web components using an intuitive declaration object with pre-defiend properties to configure lifecycle events, state management, and contents. ES6 template literals (or a custom template tool of your choice) replace JSX, a Virtual DOM provides fast updates, and HTML5 Custom Elements enables real-life HTML tags. This combination delivers custom element components using a slim but powerful delarative API.


Component Properties

These properties control almost eveything about the component using a decalrative literal-friendly interface:

Property Type Description
displayName String REQUIRED - the tagName of the custom element (without the vcc- prefix)
componentDidMount() Function Event: After initial .render(), now in DOM and populated
componentDidUpdate (prevProps, prevState) Function Event: new props/state, good for DOM work
componentWillMount Function Event: Before .render() no DOM children, but has state
componentWillReceiveProps (newProps) Function Event: Atrrib changed. Good for setState()
componentWillUnmount() Function Event: Invoked after DOM node removal
componentWillUpdate (newProps, newState) Function Event: about to re-render, too late for .setState()
shouldComponentUpdate (newProps, newState) Function Skip .render() by returning false
getDefaultProps() Function object or object-returning function of initial properties (attribs)
getInitialState() Function object or object-returning function of default state config (internal)
propTypes Object an object of methods used to coerce or validate matching-name props
css String CSS code used to style the module.
render() Function string-returning method that defines component's .innerHTML
events Object Specifies DOM events to be bound to methods on the component
mixins Object Object or Array of Objects used to extend the component definition
mixouts Object Object or Array of Objects used to extend the component's instance properties
proto Object Specifies Custom Element prototype, defaults to HTMLElement.prototype
renderTrigger Function a shortcut to bind to something like redux or CIA's .subscribe method, eg. renderTrigger:store.subscribe, will re-render each time the store updates
_delegate Boolean event delegation option: eg. <ul on-click=... to catch <li> clicks

Instance Methods

Each component is an Element with a few extra methods added on be default.


A function accepting a single object to be merged into the state of the component. Passing true as the 2nrd argument replaces the state instead of augmenting the state.


Calls the internal render() method to update the view with data that not did go through component.setState or component.setAttribute, such as a timer or global variable.


A shortcut to VCC itself, mainly to allow using the static helper methods inside of render() and events as this.VCC.methodName().

Instance Properties


An object of component properties. Attributes matching a prop name will update the prop with the attrib value upon changing. The initial props come from def.getDefaultProps().


The state of the component, exposed so that render() and events can read the state. Do not directly modify this object, use component.setState() instead. The default state comes from def.getInitialState().


A simple boolean flag set once the component element is attached to the dom.


A shortcut to the component definition, rarely needed, but allows run-time reading of config as well as sub-classing and cloning.

State and Props

Setting the state of a component should be done through this.setState({key: value}), which triggers the update lifecycle process and (potentially) re-renders the component. If you need to change and/or remember something during the usage of your app, it probably belongs in the state. Partial state objects you pass to setState extend the current state while whole states replace it.

Props are primarily a mechanism by which parents communicate chunks of data to children, via templating inside of .render(). However, since the component tag is inside the DOM, you might also find a need to modify it's attributes. Updating props does not update attributes, but you can use this.setAttribute("key", "testing") to change the attribute key and update props.key to "testing" in one command.

Tips and Tricks

  • Paste component definitions into the babel REPL to get code that runs in IE
  • Use helpers like VCC.classes({y:1, n:0}) and VCC.checked(obj.isActive) to cleanup templated attribs
  • Create static components (no updates/DOM interaction) using shouldComponentUpdate: Boolean.bind(null, false),
  • Don't deeply nest complex components, use VCC.Store to flatten updates instead
  • Inside of VCC.Store reducers, returning nothing has the same effect as return state;
  • VCC.Store's .dispatch('SOMETYPE) is the same as .dispatch({type: 'SOMETYPE'})
  • Inside of on-event handlers, this is the custom element and raised the event
  • The this value in template expressions is the nearest overhead custom element component
  • elm._renderer(true) forces redraw and elm._render() triggers one (w/shouldComponentUpdate, debounce, etc)
  • Catch many keycodes: switch(VCC.keys['_'+(e.which||e.keyCode)]){case 'RETURN':case 'SPACE': return false;}
  • Compare a single keycode with constants: if(VCC.keys['ESCAPE']==(e.which||e.keyCode))
  • VCC is passed to render to allow pure use (DI) of the Static Utilities: render: function(VCC)
  • The Static Utilities can be reached inside of render as this.VCC
  • All mixouts can be reached inside of render and events as this._name_: mixouts:{double:x=>x*x}, ... ${this.double(this.state.cost)}
  • You can use objects instead of functions with getInitialState:{a:1}, and getDefaultProps:{b:2},

Component Lifecycle

(These descriptions taken from

Various methods are executed at specific points in a component's lifecycle.


void componentWillMount()

Invoked once, both on the client and server, immediately before the initial rendering occurs. If you call setState within this method, render() will see the updated state and will be executed only once despite the state change.


void componentDidMount()

Invoked once, only on the client (not on the server), immediately after the initial rendering occurs. At this point in the lifecycle, you can access any refs to your children (e.g., to access the underlying DOM representation). The componentDidMount() method of child components is invoked before that of parent components.

If you want to integrate with other JavaScript frameworks, set timers using setTimeout or setInterval, or send AJAX requests, perform those operations in this method.


void componentWillReceiveProps(
  object nextProps

Invoked when a component is receiving new props. This method is not called for the initial render.

Use this as an opportunity to react to a prop transition before render() is called by updating the state using this.setState(). The old props can be accessed via this.props. Calling this.setState() within this function will not trigger an additional render.

componentWillReceiveProps: function(nextProps) {
    likesIncreasing: nextProps.likeCount > this.props.likeCount

Note: There is no analogous method componentWillReceiveState. An incoming prop transition may cause a state change, but the opposite is not true. If you need to perform operations in response to a state change, use componentWillUpdate.


boolean shouldComponentUpdate(
  object nextProps, object nextState

Invoked before rendering when new props or state are being received. This method is not called for the initial render or when forceUpdate is used.

Use this as an opportunity to return false when you're certain that the transition to the new props and state will not require a component update.

shouldComponentUpdate: function(nextProps, nextState) {
  return !==;

If shouldComponentUpdate returns false, then render() will be completely skipped until the next state change. In addition, componentWillUpdate and componentDidUpdate will not be called.

By default, shouldComponentUpdate always returns true to prevent subtle bugs when state is mutated in place, but if you are careful to always treat state as immutable and to read only from props and state in render() then you can override shouldComponentUpdate with an implementation that compares the old props and state to their replacements.

If performance is a bottleneck, especially with dozens or hundreds of components, use shouldComponentUpdate to speed up your app.


void componentWillUpdate(
  object nextProps, object nextState

Invoked immediately before rendering when new props or state are being received. This method is not called for the initial render.

Use this as an opportunity to perform preparation before an update occurs.


You cannot use this.setState() in this method. If you need to update state in response to a prop change, use componentWillReceiveProps instead.


void componentDidUpdate(
  object prevProps, object prevState

Invoked immediately after the component's updates are flushed to the DOM. This method is not called for the initial render.

Use this as an opportunity to operate on the DOM when the component has been updated.


void componentWillUnmount()

Invoked immediately before a component is unmounted from the DOM.

Perform any necessary cleanup in this method, such as invalidating timers or cleaning up any DOM elements that were created in componentDidMount.

Component Events

In addition to the lifecyle events, DOM and custom events may be used.

Pre-defined DOM events

The events definition property object (or method) specifies DOM events to be bound to methods on the component. VCC automatically binds these events at element creation time. Events are written in the format {"event selector": "callback"}. The value must be the name of a method or a function. Omitting the selector binds to the component itself.

live demo

    displayName: "test",

    makeRed:   function() { = "red";	},
    makeBlue:  function() { = "blue";	},
    makeGreen: function() { = "green";	},

    events: {
        "dblclick":	"makeRed",
        "click b": 	"makeBlue",
        "contextmenu .blue": "makeGreen"

    render: function() {
        return `Double-click for Red. <b class=blue > Click here for blue, right click for green.</b>.`;

on-click vs onclick

on-event-type events are synthetic and delegated. One event on the component watches all sub-tags for such events. Synthetic events vary from DOM events in that the this value is always the component, not the sub-tag that triggered the event. You can also use the word event inline in such atribs to refer to the event object, so is the sub-tag that triggered the event. Lastly, there is a shortcut to called $1, named after the console placeholder. Live Event Demo

Custom Events

Since DOM events, including custom events, bubble up to <html>, custom events are a great way to talk to parent components and containers. VCC.trigger(elm, strEvent) will dispatch an event of type strEvent on the elm Element, which will also fire on all parent elements. Custom Event Live Demo


VCC currently ships with a few common addons statically defined:

  • VCC.PureRenderMixin: defines shouldComponentUpdate() with a shallow compare on the state and props
  • VCC.shallowCompare(this, newProps, newState) : checks shallow equality on props/nextProps and state/nextState
  • VCC.LinkedStateMixin: Declaritvely 2-way binds value changes to component state <input link-state=myprop />

Static Utilities

Handy app and ES6 template helpers to reduce the boilerplate of pure JS logic

  • VCC.$(css, root) - gets Array of tags matching selectors under root (opt) or <html>

  • VCC._(arrLike) - returns a true array froma collection, string, etc

  • VCC.attrs(obj) - serializes an object into a string of HTML attributes

  • VCC.checked(val) - if v is ==true, outputs checked else outputs and empty string

  • VCC.classes(obj) - returns space-separated list of object key names whose values ==true

  • VCC.css(strCSS) - unique inject CSS with a buffered heap. Pass same CSS + , true to remove

  •, obj) - gets or sets one or more data- attribs as an object

  • VCC.elm(obj)- returns an Element from a lossless JS object defining the markups as follows:

    $:"tagName" and _:[children] are special, all other properties define attributes.

VCC.elm({ $: "div", class: "main", _: [
    "Hello ", {$: "b",_: [
turns into:  (whitespace exagerated)
<div class=main>
  • - same as VCC.elm but returns a string instead of an Element.
  • VCC.hasRoute(route, strIfFalse) - uses location.hash to match a String or RegExp route name
  • VCC.getRoute(route) - match location.hash w/ String/RX name of a key=value pair to get value
  • - if not ==true, then returns " hidden ", else returns an empty string
  • VCC.if(val) - if not ==true, then returns " hidden ", else returns an empty string
  • VCC.hide(val) - if not ==false, then returns " hidden ", else returns an empty string
  • VCC.else(val) - if not ==false, then returns " hidden ", else returns an empty string
  • VCC.trigger(elm, evt) - given Element and String event name, raise that event on the element.
  • VCC.json([val]) - unified JSON helper turns non-strings into strings, or strings and fetch responses into objects
  • VCC.orderBy(key) - returns a sort() callback function targeting a root key by name. arr.sort(VCC.orderBy("lastName"))

Static Components

Activated by setting _static: true, in a component definition, static components render extremely fast by running on a lightweight subset of the full VCC API. This partially solves the drawbacks associated with the polyfill version of document.registerElement VCC uses in some browsers, and allows all browsers to render fast and simple sub-components. Only the options listed below will be applied to the component.

Static components do not update once rendered (instead, they are cheap to render) so they don't need methods like shouldComponentUpdate or setState. You cannot update the state of an instance, but you can modify the value returned by initialState to activate component-wide changes on the next render, a major advantage of not having a build requirement. If a parent component changes an attrib given to the static component, that new value will show up in the render, making attributes the primary method for customizing static components.

Static Component Definition Members

Property Description
displayName String tag name of the component
getDefaultProps() Object or object-returning function of initial properties (attribs)
getInitialState() Object or object-returning function of default state config (internal)
componentWillMount Event: Before .render() (no DOM children)
mixins Object or Array of Objects used to extend the component definition
render() String-returning method that defines component's .innerHTML

Static Component Instance Members

Property Desription
this the lightweight instance object with {props, state, displayName, content} members
props object of properties, typically for late-specified data
state object of view state
displayName the tag name of the component (inherited from def)

Example Static Component:

    _static: 	true,
    displayName: 	"date",
    render: 	function() { 
        return new Date( +this.content || this.content ).toLocaleDateString(); 

This component formats a Date instance into a human-readable date (no time). Live Demo


React has some great ideas, but needs build tools and a large runtime, and web components don't.
Web Components also use existing, standardized syntax like <li class=item> instead of <li className=item>, reduing the re-learning needed to use it. VCC is made of lifecycle events, a VDOM-based differ, and a few helpers; all your work is done in JS, with the syntax, style, and libraries of your choice riding along as needed.

If you're not familiar with react or the VDOM concept, check it out. The main advantage is that you can write simple full-page templates like we did with PHP 10 years ago, but that those templates can update w/o UX side-effects as views are instantly merged with the user's screen. This keeps all the moving parts updated with simple logic instead of an untenable heap of DOM calls.

Differences from React

  • no JSX, returns a string of HTML from render()
  • render: is optional since not all tags need to template content.
  • component tags themselves appears in the DOM as a real tag (via Custom Element)
  • no built-in spreading props from JSX, but you can inject strings anywhere in HTML
  • no react-id or other unique IDs cluttering your clean HTML5 markup
  • no built-in helpers for propTypes on definition, use any function to coerce/default/throw as needed
  • no .statics available on definition (not that useful anyway, since it's instantiated via HTML)
  • displayName on definition is REQUIRED to defines the tagName
  • no ref String support, but does accept Functions (which are recommended)
  • tag names must use a vcc- prefix and no uppercase letters to conform with HTML5 Custom Elements
  • since it appears in the DOM, setting a component's attributes at run-time is ok, and updates props

General Conversion Routine

It's easy to convert demos from React to VCC by making a few simple syntax adjustments to bring JSX in line with HTML5.

  • change the tag wrappers in render() return from ( and ) to ` (both sides)
  • add ` "quotes" around JSX literals used in any methods, so as to create legit Strings
  • change the JS delimiters from {...} to ${...} so as to use native ES6 templating
  • change custom tags from CamelCase to lowercase, then prefix vcc- to enable it as a custom element
  • change the CamelCase event attributes (like onClick) to lowercase with an on- prefix (like on-click)
  • change React.createClass to VCC and add/modify the displayName property to custom tag name

W3 to React Life Cycle Events

Web component events provide enough unerpinning to provide customary component lifecycle events:

Web Component Event VCC Event(s)
createdCallback componentWillMount
attachedCallback componentDidMount
detachedCallback componentWillUnmount
attributeChangedCallback componentWillReceiveProps


So this all looks really neat, but what's the catch from not having a build step?

To run at max power document.registerElement() must be supported by the browser. The included polyfill is not perfect and has one important behavior difference compared to native support: the polyfill doesn't immediately (sync) populate the contents of nested components (child html mods made during componentWillMount).

This causes the VDOM's DIFF to compare un-initialized tags. While it still works because props will persist and the sub-components will self-init when they hit the DOM, it causes over-rendering compared to a browser with native web components support. Simple nested components like date formatters or pluralizers should run fast enough in all browsers, but don't wrap an extra container tag around a huge grid component. This is the main drawback and is an area of intense research to find a cure.

TLDR; if you need to run something complex at top-speed in non-webkit, don't nest complex components.
You don't need to nest VCC components at all if you use or something like redux or CIA to talk between all the pieces of your app.


Hello World Example

  displayName: "hello",
  render: function() {
    return `<h1>Hello ${}</h1>`;

+<vcc-hello name="World"></vcc-hello> =

<vcc-hello name="World"><h1>Hello World</h1></vcc-hello>

Pausable Clock Example

This example uses a click event and state management to show a pausable clock to the user: Live Demo of clock example

    displayName: 'clock',
    componentWillMount: function(){
    getInitialState: function() {
        return {
            interval: 0
    render: function() {
        return new Date()
            this.state.interval ? 
                "black" : 
    onclick: function(e) {
        var me = this.state;
        if (me.interval) this.setState({
            interval: clearInterval(me.interval)
        else this.setState({
            interval: setInterval(this.setState, 1000)

Store Example

This example uses VCC.Store to connect many comonent states in a non-conflicting manner: Live Demo of Store example

<h1>VCC Store Demo</h1>

a <vcc-setnum name=a></vcc-setnum> <br> +<br>
b <vcc-setnum name=b></vcc-setnum> <br> =<br> 
c <vcc-setnum name=c></vcc-setnum>  

<script src=></script>

var store=VCC.Store({
    SET_A: (state,e)=> state.c=state.b+(state.a=e.n),
    SET_B: (state,e)=> state.c=state.a+(state.b=e.n),
    SET_C: (state,e)=>{  state.a=e.n-state.b; state.c=e.n;  },
    a: 0,
    b: 0,
    c: 0

    displayName: "setnum",
    renderTrigger: store.subscribe.bind(store),
    setIt: function(e){
        store.dispatch({type: "SET_", n:});
    render: function(){ var s=store.getState();
        return "<input type=number on-input=this.setIt value="+s[]+">";


You might recognize the pattern as redux, which VCC.Store is a very basic implimentation of.

Mustache Example

VCC doesn't have to use ES6 templating, you can use any or even no template engine. The only requirement of .render() is that it returns a String. This example replicates the rating widget using the popular mustache.js templater instead of ES6.

Live Demo of Mustache Templates

<vcc-rate value=2></vcc-rate>  
<script type=template id=tmpStars>
  <span class=star title=1>★</span>
  <span class=star title=2>★</span>
  <span class=star title=3>★</span>
  <span class=star title=4>★</span>
  <span class=star title=5>★</span>
  <small>( {{props.value}} )</small>
<script src=""></script>
<script src=""></script>  

    displayName: 'rate',
        template: Mustache.to_html.bind(Mustache), 
        contents: document.getElementById("tmpStars").textContent
    render: function(){
        return this.template(this.contents, this);
    onclick: function(e) {
    css:`vcc-rate .star {
            transition:500ms 50ms color;
        vcc-rate small { font-size: 65%; position: relative; top: -0.2em; }
        vcc-rate[value]:hover>.star[title] {color:#111;}
        html body vcc-rate[value]:hover>.star[title]:hover ~ span[title] {color:#ccc;}

        vcc-rate[value='1'] .star:first-child ~ span, 
        vcc-rate[value='2'] .star[title='2'] ~ span, 
        vcc-rate[value='3'] .star[title='3'] ~ span, 
        vcc-rate[value='4'] .star[title='4'] ~ span {

Isomorphic Example

This example uses php file to pre-populate the data for SEO and better percieved performance: Live Demo of isomprphic example


$zip = 1 * $_GET['zip']; // validate input to be a number to stop XSS
if(!$zip) $zip = 90210;
$data = json_decode(file_get_contents('' . $zip ));

?><!doctype html>
    <meta charset="UTF-8">
    <title>Isomorphic VCC Application Demo</title>
    <link rel=stylesheet href="//" >	
</head><body class=container>
<h1>Isomorphic <a href="">VCC</a> Application Demo</h1>
<h2> App Input </h2>  
        Zip Code: <input onchange="card.setAttribute('zip', value)" value="<? echo $zip;?>" list=zips >
    <button  class=btn-success>Change</button>
    <!-- pre-populate some zip codes to tryout: -->
    <datalist id=zips>
<h2> App Output</h2>
    <vcc-zip id=card zip="<? echo $zip; ?>"> 
        The zip code <? echo $zip;?> is in the state of  <? echo $data->places[0]->state;?>

This page is pre-populated with data from <a href=isomorphic.php.txt>a php file</a>, then the client takes over state management.   
A <a href=>mustache template</a> can be used to share a template between <a href=>PHP</a> and <a href=>JS</a>, but the pay-off for a simple example like this is minimal.
<script src=></script>
    displayName: "zip",
    getInitialState: function(){
        return {
            data: <? echo json_encode($data->places[0]);?>		  	
    componentWillReceiveProps: function(newProps){
        history.replaceState(null, null, "?zip=" +;
        fetch("" +	
         .then(function(a){return a.json()})	
         .then(function(a){this.setState({ data: a.places[0] });}.bind(this));		  
    render: function(){ 
        return  " The zip code " + + " is in the state of  " +;


Instructional Demos

( adapted from a series of informative react demos ) by ruanyf

You can also run/tweak/destroy demo04 in an editable online pagedemo

  1. Render HTML
  2. Use JavaScript in HTML
  3. Use array in HTML
  4. Define a component
  5. this.props.innerHTML
  6. PropTypes
  7. Finding a DOM node
  8. this.state
  9. Form
  10. Component Lifecycle
  11. Ajax
  12. Display value from a Promise

Demo01: Render HTML (source) (live)

The template syntax in VCC is called HTML, as in regular HTML5. Use ES6 template literals to contain pretty (un-escaped) multi-line HTML in JS files. If you want backwards compatibility with non-ES6 browsers, use something like babel to transform your source into ES5.

note: VCC.intraHTML is the entry way to the internal VDOM-based partial updater, used to render without defining a component.

  `<h1>Hello, world!</h1>`

Demo02: Use JavaScript in HTML (source) (live)

You could also use JavaScript in HTML. It takes angle brackets (<) as the beginning of HTML syntax, and money curly brackets (${) as the beginning of JavaScript syntax.

var names = ['Alice', 'Emily', 'Kate'];

  ${ (name) {
      return `<div>Hello, ${name}!</div>`

Demo03: Use array in HTML (source) (live)

If a JavaScript variable is array, VCC will NOT implicitly concat all members of the array, so use join("") to view arrays:

var arr = [
  `<h1>Hello world!</h1>`,
  `<h2>VCC is awesome</h2>`,


Demo04: Define a component (source) (live)

VCC() creates a component class, which implements a render method to return an component instance of the class. You don't need to call new on the class in order to get an instance, just use it to define behavior of a custom HTML element.

var HelloMessage = VCC({
  displayName: "hellomessage",
  render: function() {
    return `<h1>Hello ${}</h1>`

  <vcc-hellomessage name="John"></vcc-hellomessage>

Components could have attributes, and you can use this.props.[attribute] to access them, just like of <vcc-hellomessage name="John"> is John.

Demo05: this.props.children (source) (live)

VCC uses `this.children to access a component's content.

var NotesList = VCC({
  displayName: "noteslist",
  render: function() {
    return `
        [], function (child) {
          return `<li>${child.textContent}</li>`;

Please be minded that the value of this.children has two possibilities. If the component has no children node, the value is null; If single children or multiple children nodes, an nodelist. You should be careful to handle it.

Demo06: PropTypes (source) (live)

Components have many specific attributes which are called ”props” in VCC and can be of any type, the default is String, which is how incoming prop updates from HTML5 attributes arrive.

Sometimes you need a way to control and convert these props. You don't want users have the freedom to input anything into your components.

VCC has a solution for this and it's called propTypes.

      var MyTitle = VCC({
    displayName: "mytitle",
        propTypes: {

        render: function() {
          return `<h1> ${this.props.title} </h1>`;

The above component of mytitle has a props of title. propTypes tells VCC that the title should be cast into a String. This is unlike React where propTypes serves to issue development-mode warnings, VCC actually applies the function to the incoming attribute value, reacting accordingly.To allow more than one type, use a simple custom function to handle as little or as much as needed.

Now we give Title a number value.

      var data = 123;
    // needs to defined in JS to use template expressions on the outer tag:
     main.innerHTML= `<vcc-mytitle title="${data}" ></vcc-mytitle>`;

This means the new property value is converted to a String before updating this.props. Attributes in HTML5 arrive as Strings, so handle accordingly. if you want to pass objects that don't easily stringify, use this.state instead.

Demo07: Finding a DOM node (source) (live)

Sometimes you need to reference a DOM node in a component. VCC gives you the ref attribute to find it using a callback function.

  var MyComponent = VCC({
    displayName: "mycomponent",
  handleClick: function() {
    // Explicitly focus the text input using the raw DOM API.
    if (this.myTextInput != null) {
  render: function() {
    // The ref attribute is a callback that saves a reference to the
    // component to this.myTextInput when the component is mounted.
    return `
        <input type="text" ref="function(ref){this.myTextInput = ref}" />
          value="Focus the text input"

VCC supports a special attribute that you can attach to any component. The ref attribute can be a callback function, and this callback will be executed immediately after the component is mounted. The referenced component will be passed in as a parameter, and the callback function may use the component immediately, or save the reference for future use (or both).

Demo08: this.state (source) (live)

VCC thinks of component as state machines, and uses this.state to hold component's state, getInitialState() to initialize this.state(invoked before a component is mounted), this.setState() to update this.state and re-render the component.

var LikeButton = VCC({
 displayName: "likebutton",
  getInitialState: function() {
    return {liked: false};
  handleClick: function(event) {
    this.setState({liked: !this.state.liked});
  render: function() {
    var text = this.state.liked ? 'like' : 'haven\'t liked';
    return `
      <p on-click=this.handleClick>
        You ${text} this. Click to toggle.
  <vcc-likebutton ></vcc-likebutton>

You could use component attributes to register event handlers, just like on-click, on-keydown, on-copy, etc.

Demo09: Form (source) (live)

According to VCC's design philosophy, this.state describes the state of component and is mutated via user interactions, and this.props describes the properties of component and is stable and immutable.

Since that, the value attribute of Form components, such as <input>, textarea, and <option>, is unaffected by any user input. If you wanted to access or update the value in response to user input, you could use the on-change event.

var Input = VCC({
  displayName: "input",
  getInitialState: function() {
    return {value: 'Hello!'};
  handleChange: function(event) {
  render: function () {
    var value = this.state.value;
    return `
        <input type="text" value=${value} on-change=this.handleChange />

Demo10: Component Lifecycle (source) (live)

Components have three main parts of their lifecycle: Mounting(being inserted into the DOM), Updating(being re-rendered) and Unmounting(being removed from the DOM). VCC provides hooks into these lifecycle parts. will methods are called right before something happens, and did methods which are called right after something happens.

   var Hello = VCC({
      displayName: "hello",
      getInitialState: function () {
        return {
          opacity: 1.0
       componentDidMount: function () {
        this.timer = setInterval(function () {
          var opacity = this.state.opacity;
          opacity -= 0.05;
          if (opacity < 0.1) {
            opacity = 1.0;
            opacity: opacity
        }.bind(this), 100);
       render: function () {
        return `
          <div style="opacity: ${this.state.opacity}">
            Hello ${}
  <vcc-hello name="world"></vcc-hello>

The following is a list of lifecycle methods.

  • componentWillMount(): Fired once, before initial rendering occurs. Good place to wire-up message listeners. this.setState doesn't work here.
  • componentDidMount(): Fired once, after initial rendering occurs. Can use this.getDOMNode().
  • componentWillUpdate(object nextProps, object nextState): Fired after the component's updates are made to the DOM. Can use this.getDOMNode() for updates.
  • componentDidUpdate(object prevProps, object prevState): Invoked immediately after the component's updates are flushed to the DOM. This method is not called for the initial render. Use this as an opportunity to operate on the DOM when the component has been updated.
  • componentWillUnmount(): Fired immediately before a component is unmounted from the DOM. Good place to remove message listeners or general clean up.
  • componentWillReceiveProps(object nextProps): !NA! (for now) Fired when a component is receiving new props. You might want to this.setState depending on the props.
  • shouldComponentUpdate(object nextProps, object nextState): Fired before rendering when new props or state are received. return false if you know an update isn't needed.

Demo11: Ajax (source) (live)

How to get the data of a component from a server or an API provider? The answer is using Ajax to fetch data in the event handler of componentDidMount. When the server response arrives, store the data with this.setState() to trigger a re-render of your UI.

var UserGist = VCC({
  displayName: "usergist",
  getInitialState: function() {
    return {
      username: '',
      lastGistUrl: ''

  componentDidMount: function() {
    $.get(this.props.source, function(result) {
      var lastGist = result[0];
      if (this.isMounted()) {
          username: lastGist.owner.login,
          lastGistUrl: lastGist.html_url

  render: function() {
    return `
        ${this.state.username}'s last gist is
        <a href=${this.state.lastGistUrl}>here</a>.
  <vcc-usergist source="" ></vcc-usergist>

Demo12: Display value from a Promise (source) (live)

This demo is inspired by Nat Pryce's article "Higher Order React Components".

If a VCC component's data is received asynchronously, we can use a Promise object as the component's property.

The above code takes data from Github's API, and the RepoList component gets a Promise object as its property.

Now, while the promise is pending, the component displays a loading indicator. When the promise is resolved successfully, the component displays a list of repository information. If the promise is rejected, the component displays an error message.

  var RepoList = VCC({
  displayName: "repolist",
  getInitialState: function() {
    return {
      loading: true,
      error: null,
      data: null

  componentDidMount() {
      value => this.setState({loading: false, data: value}),
      error => this.setState({loading: false, error: error}));

  render: function() {
    if (this.state.loading) {
      return `<span>Loading...</span>`;
    else if (this.state.error !== null) {
      return `<span>Error: ${this.state.error.message}</span>`;
    else {
      var repos =;
      var repoList = (repo) {
        return `
          <li><a href=${repo.html_url}>${}</a> (${repo.stargazers_count} stars) <br/> ${repo.description}</li>
      return `
          <h1>Most Popular JavaScript Projects in Github</h1>
   <vcc-repolist promise="$.getJSON('')" ></vcc-repolist>