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https://github.com/monkeymars/handlebars.js


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README 

        
[![Build Status](https://travis-ci.org/wycats/handlebars.js.png?branch=master)](https://travis-ci.org/wycats/handlebars.js)



Handlebars.js

=============



Handlebars.js is an extension to the [Mustache templating

language](http://mustache.github.com/) created by Chris Wanstrath.

Handlebars.js and Mustache are both logicless templating languages that

keep the view and the code separated like we all know they should be.



Checkout the official Handlebars docs site at

[http://www.handlebarsjs.com](http://www.handlebarsjs.com).



Installing

----------

Installing Handlebars is easy. Simply download the package [from the

official site](http://handlebarsjs.com/) and add it to your web pages

(you should usually use the most recent version).



Alternatively, if you prefer having the latest version of handlebars from

the 'master' branch, passing builds of the 'master' branch are automatically

published to S3. You may download the latest passing master build by grabbing

a `handlebars-latest.js` file from the [builds page][builds-page]. When the

build is published, it is also available as a `handlebars-gitSHA.js` file on

the builds page if you need a version to refer to others.

`handlebars-runtime.js` builds are also available.



**Note**: The S3 builds page is provided as a convenience for the community,

but you should not use it for hosting Handlebars in production.



Usage

-----

In general, the syntax of Handlebars.js templates is a superset

of Mustache templates. For basic syntax, check out the [Mustache

manpage](http://mustache.github.com/mustache.5.html).



Once you have a template, use the `Handlebars.compile` method to compile

the template into a function. The generated function takes a context

argument, which will be used to render the template.



```js

var source = "
Hello, my name is {{name}}. I am from {{hometown}}. I have " +

             "{{kids.length}} kids:
" +

             "
    {{#kids}}
  • {{name}} is {{age}}
    • {{/kids}}
";

var template = Handlebars.compile(source);



var data = { "name": "Alan", "hometown": "Somewhere, TX",

             "kids": [{"name": "Jimmy", "age": "12"}, {"name": "Sally", "age": "4"}]};

var result = template(data);



// Would render:

// 
Hello, my name is Alan. I am from Somewhere, TX. I have 2 kids:


// 
    

    //   
  • Jimmy is 12
    • 

    //   
  • Sally is 4
    • 

    // 


```



Registering Helpers

-------------------



You can register helpers that Handlebars will use when evaluating your

template. Here's an example, which assumes that your objects have a URL

embedded in them, as well as the text for a link:



```js

Handlebars.registerHelper('link_to', function() {

  return "" + this.body + "";

});



var context = { posts: [{url: "/hello-world", body: "Hello World!"}] };

var source = "
    {{#posts}}
  • {{{link_to}}}
    • {{/posts}}
"



var template = Handlebars.compile(source);

template(context);



// Would render:

//

// 


```



Helpers take precedence over fields defined on the context. To access a field

that is masked by a helper, a path reference may be used. In the example above

a field named `link_to` on the `context` object would be referenced using:



```

{{./link_to}}

```



Escaping

--------



By default, the `{{expression}}` syntax will escape its contents. This

helps to protect you against accidental XSS problems caused by malicious

data passed from the server as JSON.



To explicitly *not* escape the contents, use the triple-mustache

(`{{{}}}`). You have seen this used in the above example.



Differences Between Handlebars.js and Mustache

----------------------------------------------

Handlebars.js adds a couple of additional features to make writing

templates easier and also changes a tiny detail of how partials work.



### Paths



Handlebars.js supports an extended expression syntax that we call paths.

Paths are made up of typical expressions and . characters. Expressions

allow you to not only display data from the current context, but to

display data from contexts that are descendants and ancestors of the

current context.



To display data from descendant contexts, use the `.` character. So, for

example, if your data were structured like:



```js

var data = {"person": { "name": "Alan" }, "company": {"name": "Rad, Inc." } };

```



You could display the person's name from the top-level context with the

following expression:



```

{{person.name}}

```



You can backtrack using `../`. For example, if you've already traversed

into the person object you could still display the company's name with

an expression like `{{../company.name}}`, so:



```

{{#person}}{{name}} - {{../company.name}}{{/person}}

```



would render:



```

Alan - Rad, Inc.

```



### Strings



When calling a helper, you can pass paths or Strings as parameters. For

instance:



```js

Handlebars.registerHelper('link_to', function(title, options) {

  return "" + title + "!"

});



var context = { posts: [{url: "/hello-world", body: "Hello World!"}] };

var source = '
    {{#posts}}
  • {{{link_to "Post"}}}
    • {{/posts}}
'



var template = Handlebars.compile(source);

template(context);



// Would render:

//

// 


```



When you pass a String as a parameter to a helper, the literal String

gets passed to the helper function.



### Block Helpers



Handlebars.js also adds the ability to define block helpers. Block

helpers are functions that can be called from anywhere in the template.

Here's an example:



```js

var source = "
    {{#people}}
  • {{#link}}{{name}}{{/link}}
    • {{/people}}
";

Handlebars.registerHelper('link', function(options) {

  return '' + options.fn(this) + '';

});

var template = Handlebars.compile(source);



var data = { "people": [

    { "name": "Alan", "id": 1 },

    { "name": "Yehuda", "id": 2 }

  ]};

template(data);



// Should render:

// 


```



Whenever the block helper is called it is given one or more parameters,

any arguments that are passed in the helper in the call and an `options`

object containing the `fn` function which executes the block's child.

The block's current context may be accessed through `this`.



Block helpers have the same syntax as mustache sections but should not be

confused with one another. Sections are akin to an implicit `each` or

`with` statement depending on the input data and helpers are explicit

pieces of code that are free to implement whatever behavior they like.

The [mustache spec](http://mustache.github.io/mustache.5.html)

defines the exact behavior of sections. In the case of name conflicts,

helpers are given priority.



### Partials



You can register additional templates as partials, which will be used by

Handlebars when it encounters a partial (`{{> partialName}}`). Partials

can either be String templates or compiled template functions. Here's an

example:



```js

var source = "
    {{#people}}
  • {{> link}}
    • {{/people}}
";



Handlebars.registerPartial('link', '{{name}}')

var template = Handlebars.compile(source);



var data = { "people": [

    { "name": "Alan", "id": 1 },

    { "name": "Yehuda", "id": 2 }

  ]};



template(data);



// Should render:

// 


```



### Comments



You can add comments to your templates with the following syntax:



```js

{{! This is a comment }}

```



You can also use real html comments if you want them to end up in the output.



```html



    {{! This comment will not end up in the output }}

    



```



Precompiling Templates

----------------------



Handlebars allows templates to be precompiled and included as javascript

code rather than the handlebars template allowing for faster startup time.



### Installation

The precompiler script may be installed via npm using the `npm install -g handlebars`

command.



### Usage




Precompile handlebar templates.

Usage: handlebars template...



Options:

  -a, --amd            Create an AMD format function (allows loading with RequireJS)          [boolean]

  -f, --output         Output File                                                            [string]

  -k, --known          Known helpers                                                          [string]

  -o, --knownOnly      Known helpers only                                                     [boolean]

  -m, --min            Minimize output                                                        [boolean]

  -s, --simple         Output template function only.                                         [boolean]

  -r, --root           Template root. Base value that will be stripped from template names.   [string]

  -c, --commonjs       Exports CommonJS style, path to Handlebars module                      [string]

  -h, --handlebarPath  Path to handlebar.js (only valid for amd-style)                        [string]

  -n, --namespace      Template namespace                                                     [string]

  -p, --partial        Compiling a partial template                                           [boolean]

  -d, --data           Include data when compiling                                            [boolean]

  -e, --extension      Template extension.                                                    [string]

  -b, --bom            Removes the BOM (Byte Order Mark) from the beginning of the templates. [boolean]




If using the precompiler's normal mode, the resulting templates will be

stored to the `Handlebars.templates` object using the relative template

name sans the extension. These templates may be executed in the same

manner as templates.



If using the simple mode the precompiler will generate a single

javascript method. To execute this method it must be passed to the using

the `Handlebars.template` method and the resulting object may be as

normal.



### Optimizations



- Rather than using the full _handlebars.js_ library, implementations that

  do not need to compile templates at runtime may include _handlebars.runtime.js_

  whose min+gzip size is approximately 1k.

- If a helper is known to exist in the target environment they may be defined

  using the `--known name` argument may be used to optimize accesses to these

  helpers for size and speed.

- When all helpers are known in advance the `--knownOnly` argument may be used

  to optimize all block helper references.



Supported Environments

----------------------



Handlebars has been designed to work in any ECMAScript 3 environment. This includes



- Node.js

- Chrome

- Firefox

- Safari 5+

- Opera 11+

- IE 6+



Older versions and other runtimes are likely to work but have not been formally

tested.



Performance

-----------



In a rough performance test, precompiled Handlebars.js templates (in

the original version of Handlebars.js) rendered in about half the

time of Mustache templates. It would be a shame if it were any other

way, since they were precompiled, but the difference in architecture

does have some big performance advantages. Justin Marney, a.k.a.

[gotascii](http://github.com/gotascii), confirmed that with an

[independent test](http://sorescode.com/2010/09/12/benchmarks.html). The

rewritten Handlebars (current version) is faster than the old version,

and we will have some benchmarks in the near future.



Building

--------



To build handlebars, just run `rake build`, and you will get two files

in the `dist` directory.



Upgrading

---------



See [release-notes.md](https://github.com/wycats/handlebars.js/blob/master/release-notes.md) for upgrade notes.



Known Issues

------------

* Handlebars.js can be cryptic when there's an error while rendering.

* Using a variable, helper, or partial named `class` causes errors in IE browsers. (Instead, use `className`)



Handlebars in the Wild

-----------------

* [jblotus](http://github.com/jblotus) created [http://tryhandlebarsjs.com](http://tryhandlebarsjs.com)

  for anyone who would like to try out Handlebars.js in their browser.

* Don Park wrote an Express.js view engine adapter for Handlebars.js called

  [hbs](http://github.com/donpark/hbs).

* [sammy.js](http://github.com/quirkey/sammy) by Aaron Quint, a.k.a. quirkey,

  supports Handlebars.js as one of its template plugins.

* [SproutCore](http://www.sproutcore.com) uses Handlebars.js as its main

  templating engine, extending it with automatic data binding support.

* [Ember.js](http://www.emberjs.com) makes Handlebars.js the primary way to

  structure your views, also with automatic data binding support.

* Les Hill (@leshill) wrote a Rails Asset Pipeline gem named

  [handlebars_assets](http://github.com/leshill/handlebars_assets).

* [Gist about Synchronous and asynchronous loading of external handlebars templates](https://gist.github.com/2287070)

* [Lumbar](walmartlabs.github.io/lumbar) provides easy module-based template management for handlebars projects.

* [YUI](http://yuilibrary.com/yui/docs/handlebars/) implements a port of handlebars

* This [jQuery plugin](http://71104.github.io/jquery-handlebars/) allows you to use Handlebars.js with [jQuery](http://jquery.com/).



Have a project using Handlebars? Send us a [pull request](https://github.com/wycats/handlebars.js/pull/new/master)!



Helping Out

-----------

To build Handlebars.js you'll need a few things installed.



* Node.js

* Ruby

* Rake



There's a Gemfile in the repo, so you can run `bundle` to install rake

if you've got bundler installed.



To build Handlebars.js from scratch, you'll want to run `rake build`

in the root of the project. That will build Handlebars and output the

results to the dist/ folder. To run tests, run `rake spec` or `npm test`.

You can also run our set of benchmarks with `rake bench`.



If you notice any problems, please report them to the GitHub issue tracker at

[http://github.com/wycats/handlebars.js/issues](http://github.com/wycats/handlebars.js/issues).

Feel free to contact commondream or wycats through GitHub with any other

questions or feature requests. To submit changes fork the project and

send a pull request.



License

-------

Handlebars.js is released under the MIT license.



[builds-page]: http://builds.handlebarsjs.com.s3.amazonaws.com/index.html