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koa-hbs

Handlebars Templates via for Koa

Usage

koa-hbs is middleware. We stash an instance of koa-hbs for you in the library so you don't have to manage it separately. Configure the default instance by passing an options hash to #middleware. To render a template then, just yield this.render('templateName');. Here's a basic app demonstrating all that:

var koa = require('koa');
var hbs = require('koa-hbs');

var app = koa();

// koa-hbs is middleware. `use` it before you want to render a view
app.use(hbs.middleware({
  viewPath: __dirname + '/views'
}));

// Render is attached to the koa context. Call `this.render` in your middleware
// to attach rendered html to the koa response body.
app.use(function *() {
  yield this.render('main', {title: 'koa-hbs'});
})

app.listen(3000);

After a template has been rendered, the template function is cached. #render accepts two arguements - the template to render, and an object containing local variables to be inserted into the template. The result is assigned to Koa's this.response.body.

Registering Helpers

Helpers are registered using the #registerHelper method. Here is an example using the default instance (helper stolen from official Handlebars docs:

hbs = require('koa-hbs');

hbs.registerHelper('link', function(text, url) {
  text = hbs.Utils.escapeExpression(text);
  url  = hbs.Utils.escapeExpression(url);

  var result = '<a href="' + url + '">' + text + '</a>';

  return new hbs.SafeString(result);
});

registerHelper, Utils, and SafeString all proxy to an internal Handlebars instance. If passing an alternative instance of Handlebars to the middleware configurator, make sure to do so before registering helpers via the koa-hbs proxy of the above functions, or just register your helpers directly via your Handlebars instance.

Registering Partials

The simple way to register partials is to stick them all in a directory, and pass the partialsPath option when generating the middleware. Say your views are in ./views, and your partials are in ./views/partials. Configuring the middleware via

app.use(hbs.middleware({
  viewPath: __dirname + '/views',
  partialsPath: __dirname + '/views/partials'
}));

will cause them to be automatically registered. Alternatively, you may register partials one at a time by calling hbs.registerPartial which proxies to the cached handlebars #registerPartial method.

Layouts

Passing defaultLayout with the a layout name will cause all templates to be inserted into the {{{body}}} expression of the layout. This might look like the following.

<!DOCTYPE html>
<html>
<head>
  <title>{{title}}</title>
</head>
<body>
  {{{body}}}
</body>
</html>

In addition to, or alternatively, you may specify a layout to render a template into. Simply specify {{!< layoutName }} somewhere in your template. koa-hbs will load your layout from layoutsPath if defined, or from viewPath otherwise.

At this time, only a single content block ({{{body}}}) is supported.

Block content

Reserve areas in a layout by using the block helper like so.

{{#block "sidebar"}}
  <!-- default content for the sidebar block -->
{{/block}}

Then in a template, use the contentFor helper to render content into the block.

{{#contentFor "sidebar"}}
  <aside>
    <h2>{{sidebarTitleLocal}}</h2>
    <p>{{sidebarContentLocal}}</p>
  </aside>
{{/contentFor}}

Options

The plan for koa-hbs is to offer identical functionality as express-hbs (eventaully). These options are supported now.

viewPath: [required] Full path from which to load templates (Array|String)
handlebars: Pass your own instance of handlebars
templateOptions: Hash of handlebars options to pass to template()
extname: Alter the default template extension (default: '.hbs')
partialsPath: Full path to partials directory (Array|String)
defaultLayout: Name of the default layout
layoutsPath: Full path to layouts directory (String)
contentHelperName: Alter contentFor helper name
blockHelperName: Alter block helper name

Example

You can run the included example via npm install koa and node --harmony app.js from the example folder.

Unsupported Features

Here's a few things koa-hbs does not plan to support unless someone can provide really compelling justification.

Async Helpers

koa-hbs does not support asynchronous helpers. No, really - just load your data before rendering a view. This helps on performance and separation of concerns in your app.

Disable template caching

For performance reasons, this feature is not supported. The render pipeline is pretty lean right now because there isn't much branching logic. There is probably a way to do this without much overhead, but due to tools like Grunt which can just reload your app when a template changes, what's the point?

Credits

Functionality and code were inspired/taken from express-hbs.

README.md