koa-hbs 
Handlebars templates for Koa
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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 arguments - 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.
Options
The plan for koa-hbs is to offer identical functionality as express-hbs (eventaully). These options are supported now.
viewPath required
Type: Array|String
Full path from which to load templates
handlebars
Type:Object:Handlebars
Pass your own instance of handlebars
templateOptions
Type: Object
Hash of handlebars options to
pass to template()
extname
Type:String
Alter the default template extension (default: '.hbs')
partialsPath
Type:Array|String
Full path to partials directory
defaultLayout
Type:String
Name of the default layout
layoutsPath
Type:String
Full path to layouts directory
contentHelperName
Type:String
Alter contentFor helper name
blockHelperName
Type:String
Alter block helper name
disableCache
Type:Boolean
Disable template caching
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);
});Your helper is then accessible in all views by using, {{link "Google" "http://google.com"}}
The registerHelper, Utils, and SafeString methods 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.
You can also access the current Koa context in your helper. If you want to have
a helper that outputs the current URL, you could write a helper like the following
and call it in any template as {{requestURL}}.
hbs.registerHelper('requestURL', function() {
var url = hbs.templateOptions.data.koa.request.url;
return url;
});
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. If viewPath is set to an Array of paths, the first path in the
array will be assumed to contain the layout named.
At this time, only a single content block ({{{body}}}) is supported.
Overriding Layouts using Locals
As of version 0.9.0, it's possible to override the layout used for rendering,
using locals. For example:
router.get('/', function *() {
yield this.render('foo', {
layout: 'bar'
});
});See the tests for more.
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}}Disable Template Caching
To disable the caching of templates and partials, use the disableCache option.
Set this option to true to disable caching. Default is false.
Remember to set this option to false for production environments, or performance
could be impacted!
Locals
Application local variables ([this.state](https://github.com/koajs/koa/blob/master/docs/api/context.md#ctxstate)) are provided to all templates rendered within the application.
app.use(function *(next) {
this.state.title = 'My App';
this.state.email = '[email protected]';
yield next;
});The state object is a JavaScript Object. The properties added to it will be exposed as local variables within your views.
<title>{{title}}</title>
<p>Contact : {{email}}</p>
Koa2
Koa2 is supported via the @next module version. It is considered experimental
and requires Node v7 or higher. You can obtain this version by running:
npm install koa-hbs@next --saveFor information on using this version, please read the branch's
README. If using a version of
node older than v7.6, we recommend using
harmonica to enable the --harmony
flags, which activates native async/await support.
If you'd rather not use an experimental version, or you need to use an older
version of Node, you can reference this example
repo that demonstrates how to use koa-hbs with Koa2:
koa-hbs-koa2-howto
Credit to @chrisveness for the initial investigation.
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.
Handlebars Version
As of [email protected], the version of the Handlebars dependency bundled with this module has been updated to 4.0.x. If this causes conflicts for your project, you may pass your own instance of Handlebars to the module, or downgrade to the last 0.8.x version.
Credits
Functionality and code were inspired/taken from express-hbs. Many thanks to @jwilm for authoring this middleware.