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mustache.js for Chrome Apps — Logic-less {{mustache}} templates with JavaScript that work under the CSP.

What is this?

A special build of mustache.js (by @janl) which works within the security policies defined by the Google Chrome Apps/Extensions Content Security Policy.

In CSP, inline JavaScript as well as potentially harmful string-to-JS methods such as eval are not executed. Whilst great for security, this also means that it can be a challenge finding a popular templating engine which doesn't use features disabled by the policy.

This version of mustache works fine under the CSP and has been used with frameworks such as Backbone.js within Chrome Apps without any issues.

What alternatives are available that work with Chrome Apps?

  • Pre-compiling your templates. Handlebars offers this feature and Matthew Robertson has a good post which outlines a strategy for pre-compiling templates that works with CSP. Note that with manifest_version: 2, you must use precompilation if opting for handlebars. If you try to use Handlebars.compile() you will get an error about CSP error violations.

  • Closure Templates is a templating library which also doesn't not use eval. Templates are simply compiled to JavaScript ahead of time, so that what gets included in your app is a plain .js file that should not run into CSP issues.

  • Ashe is a lightweight templating library which supports variable replacement, loops, conditions and new variables inline. It uses neither eval nor new Function

  • Distal is another templating library free of eval

  • Sandboxing eval. You have the option to use eval and new Function inside a sandboxed iframe. e.g, in the manifest one could do:

"sandbox": {
    "pages": [
      "pageA.html",
      "app/pageB.html"
    ]
},

Sandboxed pages don't have extensions, app APIs or access to pages which are non-sandboxed, but can communicate with them using postMessage(). See this example which demonstrates circumventing the problem. This example compiles Handlebar templates in a sandboxed iframe and returns the generated HTML to the caller page.

What could be more logical awesome than no logic at all?

mustache.js is an implementation of the Mustache templating system in JavaScript.

Mustache is a logic-less template syntax. It can be used for HTML, config files, source code - anything. It works by expanding tags in a template using values provided in a hash or object.

We call it "logic-less" because there are no if statements, else clauses, or for loops. Instead there are only tags. Some tags are replaced with a value, some nothing, and others a series of values.

For a language-agnostic overview of Mustache's template syntax, see the mustache(5) manpage.

Where to use mustache.js?

You can use mustache.js to render templates in many various scenarios where you can use JavaScript. For example, you can render templates in a browser, server-side using node, in CouchDB views, or in almost any other environment where you can use JavaScript.

Who uses mustache.js?

An updated list of mustache.js users is kept on the Github wiki. Add yourself or your company if you use mustache.js!

Usage

Below is quick example how to use mustache.js:

var view = {
  title: "Joe",
  calc: function() {
    return 2 + 4;
  }
};

var html = Mustache.to_html("{{title}} spends {{calc}}", view);

In this example, the Mustache.to_html function takes two parameters: 1) the mustache template and 2) a view object that contains the data and code needed to render the template.

browserify

Use mustache.js in your browser as a module using browserify

  var Mustache = require('mustache-for-chromeapps');

  var html = Mustache.to_html(...);

Template Tag Types

There are several types of tags currently implemented in mustache.js.

Simple Tags

Tags are always surrounded by mustaches like this {{foobar}}.

var view = {name: "Joe", say_hello: function(){ return "hello" }}

template = "{{say_hello}}, {{name}}"

Accessing values in nested objects (Dot Notation)

To access data logically grouped into nested objects, specify a '.' delimited path to the value.

var contact = {
  name: {first: "Bill", last: "Bobitybob" },
  age: 37
}

template = "Hello, {{name.first}} {{name.last}}. You are {{age}} years old."

NOTICE: The dot notation feature was recently implemented for the 0.4 release, which is not out as of Nov 9 2011. You can find the feature in the current master branch of mustachejs.

Conditional Sections

Conditional sections begin with {{#condition}} and end with {{/condition}}. When condition evaluates to true, the section is rendered, otherwise the whole block will output nothing at all. condition may be a function returning true/false or a simple boolean.

var view = {condition: function() {
  // [...your code goes here...]
  return true;
}}

{{#condition}}
  I will be visible if condition is true
{{/condition}}

Enumerable Sections

Enumerable Sections use the same syntax as condition sections do. {{#shopping_items}} and {{/shopping_items}}. Actually the view decides how mustache.js renders the section. If the view returns an array, it will iterator over the items. Use {{.}} to access the current item inside the enumeration section.

var view = {name: "Joe's shopping card",
            items: ["bananas", "apples"]}

var template = "{{name}}: <ul> {{#items}}<li>{{.}}</li>{{/items}} </ul>"

Outputs:
Joe's shopping card: <ul><li>bananas</li><li>apples</li></ul>

Higher Order Sections

If a section key returns a function, it will be called and passed both the unrendered block of text and a renderer convenience function.

Given this object:

"name": "Tater",
"bolder": function() {
  return function(text, render) {
    return "<b>" + render(text) + '</b>'
  }
}

And this template:

{{#bolder}}Hi {{name}}.{{/bolder}}

We'll get this output:

<b>Hi Tater.</b>

As you can see, we’re pre-processing the text in the block. This can be used to implement caching, filters (like syntax highlighting), etc.

You can use this.name to access the attribute name from your view.

Dereferencing Sections

If your data has components that are logically grouped into nested objects, you may wish to dereference an object to access its values.

Given this object:

{
  "name": "Bill",
  "address": {
    "street": "801 Streetly street",
    "city": "Boston",
    "state": "MA",
    "zip" "02101"
  }
}

And this template:

<h1>Contact: {{name}}</h1>
{{#address}}
  <p>{{street}}</p>
  <p>{{city}}, {{state}} {{zip}}</p>
{{/address}}

We'll get this output:

<h1>Contact: Bill</h1>
  <p>801 Streetly street</p>
  <p>Boston, MA 02101</p>

Inverted Sections

An inverted section opens with {{^section}} instead of {{#section}} and uses a boolean negative to evaluate. Empty arrays are considered falsy.

View:

var inverted_section =  {
  "repo": []
}

Template:

{{#repo}}<b>{{name}}</b>{{/repo}}
{{^repo}}No repos :({{/repo}}

Result:

No repos :(

View Partials

mustache.js supports a quite powerful but yet simple view partial mechanism. Use the following syntax for partials: {{>partial_name}}

var view = {
  name: "Joe",
  winnings: {
    value: 1000,
    taxed_value: function() {
        return this.value - (this.value * 0.4);
    }
  }
};

var template = "Welcome, {{name}}! {{>winnings}}"
var partials = {
  winnings: "You just won ${{value}} (which is ${{taxed_value}} after tax)"};

var output = Mustache.to_html(template, view, partials)

output will be:
Welcome, Joe! You just won $1000 (which is $600 after tax)

You invoke a partial with {{>winnings}}. Invoking the partial winnings will tell mustache.js to look for a object in the context's property winnings. It will then use that object as the context for the template found in partials for winnings.

Escaping

mustache.js does escape all values when using the standard double mustache syntax. Characters which will be escaped: & \ " ' < >. To disable escaping, simply use triple mustaches like {{{unescaped_variable}}}.

Example: Using {{variable}} inside a template for 5 > 2 will result in 5 &gt; 2, where as the usage of {{{variable}}} will result in 5 > 2.

Streaming

To stream template results out of mustache.js, you can pass an optional send() callback to the to_html() call:

Mustache.to_html(template, view, partials, function(line) {
  print(line);
});

Pragmas

Pragma tags let you alter the behaviour of mustache.js. They have the format of

{{%PRAGMANAME}}

and they accept options:

{{%PRAGMANAME option=value}}

IMPLICIT-ITERATOR

When using a block to iterate over an enumerable (Array), mustache.js expects an objects as enumerable items. The implicit iterator pragma enables optional behaviour of allowing literals as enumerable items. Consider this view:

var view = {
  foo: [1, 2, 3, 4, 5, "french"]
};

The following template can iterate over the member foo:

{{%IMPLICIT-ITERATOR}}
{{#foo}}
  {{.}}
{{/foo}}

If you don't like the dot in there, the pragma accepts an option to set your own iteration marker:

{{%IMPLICIT-ITERATOR iterator=bob}}
{{#foo}}
  {{bob}}
{{/foo}}

Plugins for JavaScript Libraries

mustache.js may be built specifically for several different client libraries and platforms, including the following:

These may be built using Rake and one of the following commands:

$ rake commonjs
$ rake jquery
$ rake dojo
$ rake yui
$ rake requirejs
$ rake qooxdoo

Thanks

Mustache.js wouldn't kick ass if it weren't for these fine souls:

  • Chris Wanstrath / defunkt
  • Alexander Lang / langalex
  • Sebastian Cohnen / tisba
  • J Chris Anderson / jchris
  • Tom Robinson / tlrobinson
  • Aaron Quint / quirkey
  • Douglas Crockford
  • Nikita Vasilyev / NV
  • Elise Wood / glytch
  • Damien Mathieu / dmathieu
  • Jakub Kuźma / qoobaa
  • Will Leinweber / will
  • dpree
  • Jason Smith / jhs
  • Aaron Gibralter / agibralter
  • Ross Boucher / boucher
  • Matt Sanford / mzsanford
  • Ben Cherry / bcherry
  • Michael Jackson / mjijackson