Modular Render Components

ZestJS provides client and server rendering for static and dynamic HTML widgets (Render Components) written as AMD modules providing low-level application modularity and portability.

  1. Write widgets as AMD Render Components, with separate template, interaction script and CSS files.
  2. Render them on the client or server with a single render call, loading them through RequireJS.
  3. Build with the RequireJS Optimizer into a single file or layers in production, including the compilation of CSS or LESS and templates.

Client Rendering

Include RequireJS and the Zest Client library (10KB minified and gzipped) in the page, then use the provided render function:

  $z.render('@app/dialog', {

    content: "<p>Welcome to ZestJS.</p>",
    width: 300,
    height: 50,
    confirmText: 'Ok'

  }, document.querySelector('.dialog-example'));

Click "run" above to see the render.

  • This loads the render component located RequireJS Module ID, app/dialog.
  • The component is then rendered with the given content, dimensions and button text.
  • It is injected into the div above with class .dialog-example.

Server Rendering

Use the provided NodeJS server module or the dedicated render server.

Click here for the example component rendered on the server.

  • The exact same component is now rendered on the server, with assets and scripts attached seamlessly.
  • The CSS blocks the HTML page render stream to show only styled widgets.
  • The dynamic attachment can optionally block the page render stream until its scripts have loaded, or it can be configured for progressive enhancement.
  • In production, scripts are loaded fully compatible with built script layers.


Components can be combined together with regions allowing for compound components. This home page is a compound render component with separate header, sidebar and content regions.

Written as a Render Component, despite this page being rendering on the server, we can re-render this home page from the client quite easily. This includes generating all the HTML from markup, attaching the scroll detection in the contents on the left and enabling the live code run buttons.

Click the run button below.

  // start preloading

  // clear the page
  document.body.scrollTop = 0;

  // render a dialog
  $z.render('@app/dialog', {

    content: "<p>Render the homepage from the client.</p>",
    width: 300,
    height: 50,
    confirmText: 'Go'

  }, document.body, function(Dialog) {

    Dialog.Button.click.on(function() {

      // render the homepage
      $z.render('@cs!site/home', document.body, function() {
        document.body.scrollTop = 1090; 


  • We completely cleared the page, then rendered a dialog.
  • On the dialog controller, we register an event to the button click.
  • When clicked, the Zest render function dynamically requested this home page component with RequireJS.
  • RequireJS handles compilation of the site CoffeeScript, LESS and Markdown dynamically.
  • Zest then rendered the page component into the body, applying the dynamic attachments predictably.

Note that in production we would never normally download the compilers to the browser, this is only useful in development as it allows us to have an efficient on-demand compilation removing the need for a development build.

Zest gives you:

  • A way of managing modular render component files with AMD.
  • Custom controller registration for interacting with dynamic components.
  • Nested component rendering with regions.
  • A natural modularity for frontend code based on controller hierarchies.
  • Natural build support through AMD including CSS or LESS, templates and attachments on both the client and server.
  • Browser support in IE7+ and the rest.

Zest doesn't give you:

  • Models or binding - the choices here are left up to you.
  • A DOM manipulation library.
  • A dictated environment - it's more of a tool and a method than a framework.

Writing Render Components

A Render Component consists of two AMD modules:

  1. A renderer which can be used to generate HTML on the client or server, while specifying CSS dependencies.
  2. An attachment which is executed on the client to add interaction to the DOM. For static components with no interaction, this can be left out.

The renderer takes the following form as an AMD module:

The use of define is the standard way of defining a JavaScript module in RequireJS (and in any AMD loader), where the first array argument specifies the dependencies for the module.


  define(['zest', 'tpl!./button', 'less!./button'], function($z, template) {
    return {

      // provide default options
      options: {
        text: 'Default Text'

      // dynamic options processing (async also supported)
      load: function(options) {
        options.text = $z.esc(options.text, 'htmlText');

      // provide the template function returning HTML
      render: template,

      // reference the attachment module
      attach: './button-controller'

  • The renderer conforms to the expected Render Component specification so it can be rendered by a $z.render call.
  • Rendering takes some options data, which gets populated with defaults or processed.
  • By making the CSS or LESS a dependency of the module, this provides client injection, server tracing and modular CSS build support.
  • A RequireJS template plugin can load a template file and return a JavaScript function to provide as the render property. A custom function or string returning HTML from the options data can also be used.

The attachment module takes the following form:


    define(['zest', 'jquery'], function($z, $) {
      // enhancement function
      return function(el, o) {

        // standard frontend code
        $(el).click(function() {
          // ...

        // returns a controller object
        return {
          method: function() {
            // controller method
  • The attachment is called on the client with the DOM element and attachment options as arguments.
  • The optional return value is a JavaScript object to be used as the controller.
  • Controllers can be found using the selector $z.select('.Button'), where the selector is a standard DOM selector, making debugging from the console straigthforward.

Try it out yourself by installing ZestJS, or to learn more about rendering from the first principles, read the Render Component Introduction.

Server Modules

Server rendering can be performed via a NodeJS API, as an HTML render service (just a like a database server), or using a Zest Server module. The HTML render service module could easily be linked into other server languages through a bridge library, providing the rendering function for other frameworks.

Zest Server modules map routes into components, which are then rendered with options from the URL.


    routes: {
      '/': {
        title: 'Example Page',
        body: '@my-component',

In all of these rendering modes, the server is configuration-based. An example configuration to run the above module would be:


    // port to run the server on
    port: 8080

    // load the application module (app.js)
    modules: ['$/app'],

    // RequireJS config - exactly as in RequireJS docs
    require: {
      // requirejs build config (exactly as in requirejs docs, but with defaults provided)
      build: {
        zestLayer: {
          include: ['^!app/my-component']

This can then be started by running the zest command at the root of the application.

Read more about rendering and server modules in the documentation.

Production Builds

When we launch, we can build all our files into one single file to load in the page, or use layered builds to have separate blocking and asynchronous layers for the page load.

Zest Server Build

For the server above, we would instead start our server with:

  zest start production

This will run the build and start the server, loading the given component from a single script, including the compiled LESS and template.

Zest Client Build

For client apps, we invoke the RequireJS Optimizer manually, using the standard optimization command:

  r.js -o build.js

An example client build is provided in the sample browser app templates.

Read more on the build process in the documentation.


Getting Started

There are two template applications provided to quickly get started with Zest.

The Zest Client Quick Start template demonstrates browser rendering and builds.

The Zest Server Quick Start template demonstrates server routing and rendering with NodeJS.

A brief introduction to rendering, server modules and builds is provided here.

For further background, read the conceptual introduction.

For the comprehensive guide to rendering, read the documentation here.

Install Zest Client

The best way to start an application is by installing one of the application templates with Volo.

Volo is a package manager that allows for creating project templates and installing project dependencies such as jQuery (volo add jquery). It's a convenient way to get started with Zest and manage project dependencies. Other package managers can also work with Zest - feel free to send a pull request.

  1. Use Volo to install the client template, by ensuring you have NodeJS installed, then installing Volo and creating the project from the template:

         npm install volo -g
         volo create myapp zestjs/template-browser

    This will download the template and all its dependencies to the 'myapp' folder.

  2. Run the app by opening up www/index.html in the browser.

This loads up RequireJS with the minimal Zest configuration, and then renders a sample component into the page.

This technique can be used to create single page apps, with all Zest rendering occurring in the browser.

CoffeeScript Template

Writing Render Components with CoffeeScript is a lot neater. To see the sample in CoffeeScript, use the version from:

    volo create myapp zestjs/template-browser-cs

The CoffeeScript template also comes with less in the sample app as well.

Next Steps

Follow the Render Component Introduction above, or read the full guided documentation.

Install Zest Server

  1. To install Zest server, install Zest and Volo as global modules (ensure you have NodeJS installed):

     npm install volo zest-server -g
  2. To create a Zest application, use Volo to automatically generate the application from the basic server template:

     volo create myapp zestjs/template-basic

    This will create a new folder called 'myapp' containing the project template, and download all the necessary Zest dependencies into the public library folder.

    • To start the template application, simply run zest from within the myapp folder:
       cd myapp
    • Alternatively, if you want to use Zest Server from within NodeJS, run the NodeJS server at:
      node ~node-server.js
  3. Navigate to http://localhost:8080/ and http://localhost:8080/test to see the site.

CoffeeScript Template

For the same template, but written as a CoffeeScript server and using LESS, use the following install command:

    volo create myapp zestjs/template-basic-cs

Next Steps

With the server installed, follow the Render Component introduction, or read the full guided documentation.


If you're stuck or have any questions, post a comment on the ZestJS Google Group.

To report issues or get involved in the development, find ZestJS on GitHub.