koa-handlebars
> A koa middleware for using handlebars templates
Last updated a year ago by dominicbarnes .
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koa-handlebars

A koa middleware for using handlebars templates

Usage

This middleware adds 2 methods to the koa context object. The primary one is render(view, locals), which automatically sets the content-type as text/html and writes the generated view as the response. There is also renderView(view, locals), which yields the raw string. This allows you to modify the response further.

app.js

var koa = require("koa");
var handlebars = require("koa-handlebars");

var app = koa();

app.use(handlebars({
  defaultLayout: "main"
}));

app.use(function *() {
  yield this.render("index", {
    title: "Test Page",
    name: "World"
  });
});

app.listen(3000);

layouts/main.hbs

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

views/index.hbs

Hello, {{name}}!

Resulting page

<!DOCTYPE html>
<html>
  <head>
    <title>Test Page</title>
  </head>
  <body>
    Hello, World!
  </body>
</html>

Views

The entry point for rendering is known as a view. The view usually contains the content specific to a single page. It has access to all loaded partials, helpers and is injected into the {{{@body}}} of the corresponding layout. (if there is one)

The simplest usage is to have a flat views/ directory that contains .hbs files. (although other patterns are possible, see the "Advanced Usage" section for more details)

In "development mode", views are not cached.

Layouts

Layouts are the content that is shared between many views. Like views, it has access to all loaded partials and helpers. The {{{@body}}} local is set as the content of the corresponding view.

The simplest usage is to have a flat layouts/ directory that contains .hbs files. (although other patterns are possible, see the "Advanced Usage" section for more details)

In "development mode", layouts are not cached.

Partials

Partials are sub-templates that you can use to render smaller bits within layouts/views.

There are 2 main types of partials. First, global partials are registered during init. (see options.partials) These will not be dynamically updated, not even during "development mode". (thus, you will need to restart your server when these globals change)

Secondly, partials residing in the directory specified by options.partialsDir will be dynamically loaded on each render call. When caching is enabled, that overhead is reduced substantially, and further optimization will be done in the future.

Helpers

Helpers are functions that any of your templates can call upon.

Currently, helpers can only be defined globally and must be declared during initialization. (see options.helpers) This requires a server restart after any changes, but this will be improved upon in the future.

Development

To enable "development mode" in your server, simply set cache: false in your middleware configuration.

In addition, this library uses visionmedia/debug, so you can enable debug output via DEBUG=koa-handlebars in the terminal.

Special Variables

When rendering templates, koa-handlebars will add 3 special private variables to your templates:

  • @body: in layouts, this is the contents of the rendererd view
  • @view: the name of the view that is being rendered
  • @layout: the name of the layout that is being rendered
  • @koa: the koa ctx of the current request

You can add more variables of your own via the data option or more dynamically with the beforeRender function. (see configuration options section for more details)

Generally speaking, avoid injecting data directly into locals from middleware, instead focus on adding things to options.data or using the koa context to grab data from there. (eg: {{@koa.request.length}})

Configuration Options

root

The base directory to use when resolving paths.

Default: process.cwd()

cache

Enables or disables the view cache. This is basically the flag for "development mode".

Default:: true

app.use(handlebars({
  cache: app.env !== "development"
}));

data

Adds additional private data (alongside @view, @layout and @koa) to the handlebars render options.

extension

The extension(s) that your template files can use. Any files not using the given extensions will be ignored.

Default: "hbs"

If you have multiple extensions, you simply use an array.

For example: [ "hbs", "handlebars", "tpl" ]

viewsDir

The location of your view templates (relative to root)

Default: "views"

viewPath(id)

Translates the given id into a path to resolve the template file. (the file extension is not required) If the returned path is relative, it will be assumed as relative to viewsDir.

By default, this simply returns the given id.

This function is run with the renderer as it's context (ie: this) so you can access this.options for advanced usage.

defaultLayout

If you are using layouts, then this can be used to bypass requiring each call to render() to specify a layout manually. Otherwise, leaving it empty will not render a layout at all unless otherwise specified.

layoutsDir

The location of your layout templates (relative to root)

Default: "layouts"

layoutPath(id)

Translates the given id into a path to resolve the template file. (the file extension is not required) If the returned path is relative, it will be assumed as relative to layoutsDir.

By default, this simply returns the given id.

This function is run with the renderer as it's context (ie: this) so you can access this.options for advanced usage.

partialsDir

The location of your non-global partial templates (relative to root)

Default: "partials"

partialId(file)

This function is a little backwards compared to layouts and views, but it takes a path for a partial template file. (relative to partialsDir) and converts it into a handlebars-friendly identifier.

For example: "navigation.hbs" => "navigation"

By default, it will strip the extension and camel-case the remaining string.

For example: "nav/main.hbs" => "navMain"

helpers

Allows you to define global helpers during initialization, this should be a shallow object where each key is a helper name and the value is a function.

partials

Allows you to define global partials during initialization, this should be a shallow object where each key is a partial name and the value is a function.

handlebars

Allows you to pass a custom handlebars instance, which you may want to do in some edge cases. For example, if you plan on using Handlebars.SafeString in your block helpers, you'll need a handle on the same instance of handlebars that the middleware is using. For example:

// app.js
var handlebars = require('handlebars');
var hbsKoa = require('koa-handlebars');

var app = koa();
app.use(hbsKoa({
  handlebars: handlebars
}));

// helpers.js

// Same instance, because node modules are cached
var Handlebars = require('handlebars');

module.exports.myHelper = function(input, options) {
  return new Handlebars.SafeString('<div class="some-html">' + input + '</div>');
};
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