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Teddy templating engine

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Teddy is the most readable and easy to learn templating language there is!

Or put a more technical way, Teddy is an easy to read, HTML-inspired, mostly logic-less DOM templating engine with support for both server-side and client-side templating.

It uses HTML-like <tags> for rudimentary templating logic and Teddy Roosevelt's facial hair for {variables}.

Teddy Roosevelt's facial hair is a curly brace.

Table of contents

Why yet another templating engine?

Good question.

Here's why:

Other popular templating engines are too cryptic

Are you tired of all those unnecessarily cryptic templating systems out there that look like this?

    <li><a href="{{url}}">{{name}}</a></li>
  <p>The list is empty.</p>

...Or this?

{{#each comments}}
<h2><a href="/posts/{{../permalink}}#{{id}}">{{title}}</a></h2>

...Or this?

{#names}{.}{@idx}{.}{/idx}{@sep}, {/sep}{/names}

Want something simpler and more readable so you can stop wasting time memorizing what all those funky symbols do and just get work done?

Well you're not the only one.

Teddy, symbol-buster extraordinaire

Teddy the trust-buster was a man of the people, curtailing the abuse of monopolists. As the most badass President of all-time, there's no way he'd put up with all this indecipherable templating nonsense.

As such, Teddy the templating engine is an engine of the people, curtailing the abuse of indecipherable templating systems. Teddy trust-buster extraordinaire is now symbol-buster extraordinaire.

Here's how:

  • More concise {variable} syntax. One curly bracket. Not two, not three, no pound signs, no question marks, no backticks, no gang signs, and no hieroglyphs.
  • An <include> tag for layout templates and partials which accepts arguments via child <arg> elements.
  • Flow control tags: <if>, <unless>, <elseif>, <elseunless>, and <else> for basic templating logic.
  • A <loop> tag for looping.
  • Server-side {!comments!} delimited by exclamation points in a fashion similar to <!-- HTML comments -->. Server-side comments are stripped out at the template compilation stage.
  • No funky symbols to memorize. Just {variables} for data and new HTML-like <tags> for rudimentary logic.

How to write Teddy templates

Here's some examples of how to write Teddy templates:


Display a variable by simply writing {varName} anywhere in the template.

HTML entities such as <, >, &, ', and " will be escaped by default as a safeguard against cross-site scripting.

If you need to suppress this escaping in certain scenarios, write your variable like this: {varName|s}.


Include another template:

<include src='partial.html'></include>

Or use the no extension shorthand (Teddy will append the .html extension for you):

<include src='partial'></include>

Pass arguments to the template:

<include src='partial.html'>
  <arg firstArgument>Plain text argument</arg>
  <arg secondArgument>
    <span>Argument with HTML in it</span>

The arguments you've defined will be accessible as {firstArgument} and {secondArgument} in the child template partial.html.


Check for the presence of a variable:

<if something>
  <p>The variable 'something' is present</p>
  <p>The variable 'something' is not present</p>

Check a variable's value:

<if something='hello'>
  <p>The variable 'something' is set to 'hello'</p>
  <p>The variable 'something' is not set to 'hello'</p>

Check for the non-presence of a variable:

<unless something>
  <p>The variable 'something' is not present</p>
  <p>The variable 'something' is present</p>

An <if> statement structure with an <elseif> tag which is evaluated if the first <if> fails:

<if something>
  <p>The variable 'something' is present</p>
<elseif somethingElse>
  <p>The variable 'something' is not present, but 'somethingElse' is present</p>
  <p>The variable 'something' is not present and neither is 'somethingElse'</p>

An <unless> statement structure with an <elseunless> tag which is evaluated if the first <unless> fails:

<unless something>
  <p>The variable 'something' is not present</p>
<elseunless somethingElse>
  <p>The variable 'something' is present, but 'somethingElse' is not present</p>
  <p>The variables 'something' and 'somethingElse' are both present</p>

Boolean logic

Boolean logic operators are evaluated left to right.

or operator:

<if something or somethingElse>
  <p>This will render if either 'something' or 'somethingElse' is present.</p>

and operator

<if something and somethingElse>
  <p>This will render if 'something' is present and 'somethingElse' is present too.</p>

xor operator:

<if something xor somethingElse>
  <p>This will render if either 'something' is present or 'somethingElse' is present, but it will not render if both are present.</p>
  <p>This will render if 'something' is present and 'somethingElse' is present too.</p>

not: prefix:

<if not:something>
  <p>This will render if 'something' is not present.</p>

One line ifs

If you need a more concise conditional just to control which attributes are applied to a given element, then use this syntax:

<p if-something true="class='present'" false="class='not-present'">One line if.</p>

In that structure, the attribute if-something checks to see if the variable something is present. If so, the class delcared in the true attribute is written to the element, resulting in the following output:

<p class='present'>One line if.</p>

If not, the class declared in the false attribute is written to the element, resulting in the following output:

<p class='not-present'>One line if.</p>

Like the <if> tag you can check for both the presence of a variable as well as its value. To check the value of a variable, use this syntax:

<p if-something='hello' true="class='hello'" false="class='not-hello'">One line if.</p>

It's important to note that whichever type of quotes you use on the outside of your true or false attributes must be reversed on the inside. So if you use single quotes on the outside, then you must use double quotes on the inside.


Assume the following JS model:

letters = ['a', 'b', 'c'];

It can be iterated over like so:

<loop through='letters' val='letter'>
  <p>{letter}</p> <!-- outputs a, b, c -->

In the above example through='letters' defines the JS model being iterated over and val='letter' defines a local variable for the current letter being iterated over.

When looping over more complex data structures, sometimes you will need access to both the key and the value of your array or object. For instance, suppose this JS model:

names = {jack: 'guy', jill: 'girl', hill: 'landscape'};

It can be iterated over like so:

<loop through='names' key='name' val='description'>
  <p>{name}</p> <!-- outputs jack, jill, hill -->
  <p>{description}</p> <!-- outputs guy, girl, landscape -->

We once again define a through attribute which we set to through='names' and a val attribute which we set to val='description' similar to the last example. However this time we've iterated over a JS object with named keys instead of a simple indexed array, so it is useful to define a key attribute in the <loop> tag to gain access to the name of the current iteration variable. We have defined it as key='name' in this example.

Even complex, hierarchical data structures can be iterated over. For instance, suppose this JS model:

objects = [{a:1, b:2, c:3}, {a:4, b:5, c:6}, {a:7, b:8, c:9}];

For the above array of objects, we can combine the techniques illustrated above to display each member of the hierarchy in sequence:

<loop through='objects' key='i' val='item'>
  <p>{i}</p> <!-- outputs 0, 1, 2 -->
  <p>{item.a}</p> <!-- outputs 1, 4, 7 -->
  <p>{item.b}</p> <!-- outputs 2, 5, 8 -->
  <p>{item.c}</p> <!-- outputs 3, 6, 9 -->

Note: you can also use in in place of through if you like a more concise syntax.

A complex example combining all tag types

Supposing the following JS model again:

objects = [{a:1, b:2, c:3}, {a:4, b:5, c:6}, {a:7, b:8, c:9}];

We could perform many complex operations simultaneously. For instance, we could iterate over it with a <loop> and then at each iteration perform an <if> statement and <include> a partial:

<loop through='objects' val='item'>
  <if item.a='4'>
    <p>item.a is 4</p>
  <p if-item.b='5' true="class='item-b-is-five'" false='hidden'>item.b is 5</p>
  <include src='partial.html'>
    <arg firstArgument>{item.b}</arg>
    <arg secondArgument>

Using Teddy in Node.js

Teddy is designed for use with Express in Node.js.

  • First require the node modules express, and teddy.
  • Then initialize express and configure it to your liking.
  • In your express config, make sure to include this line: app.engine('html', teddy.__express).

If you're looking for a more fully-featured web framework to build web apps with using Teddy templates, then try out Teddy's companion, Roosevelt.

If you're interested in using Teddy with the gulp.js build system for Node apps, check out the gulp-teddy project.

Using Teddy with client-side JS

On the client-side, pass source code to Teddy's render method, like so: teddy.render(sourceCode, yourModel). The render method will return a fully rendered template.

API documentation

  • teddy.compile(template): Compile a template by supplying either source code or a file name (in Node.js).
    • Returns template source code with {! teddy comments !} removed.
    • Populates teddy.templates with the new template in the format of teddy.templates[path]: compiledSource.
  • teddy.render(template, model): Render a template by supplying either source code or a file name (in Node.js).
    • Returns fully rendered HTML.
  • teddy.setTemplateRoot(path): Set the location of your templates directory.
    • Default is the current directory.
  • teddy.setVerbosity(n): Sets the level of verbosity in Teddy's console logs. Call teddy.setVerbosity(n) where n equals one of the below values to change the default:
    • 0: No logging.
    • 1: The default. Concise logging. Usually just logs serious errors.
    • 2: Verbose logging. Logs even minor errors.
    • 3: Debug mode. Very verbose.
  • teddy.cacheRenders(true/false): When this setting is enabled, Teddy will cache all unique combinations of templates and models. Any time a template has been rendered before with the given model, the cached template will be returned instead, improving performance.
    • Default is false. (Feature is currently experimental.)
  • teddy.setDefaultCaches(n): Set the default number of unique caches to store per template when template caching is enabled.
    • Default: 1.
  • teddy.setMaxCaches(template, n): Set the maximum number of unique caches to store for a given template when template caching is enabled.
  • teddy.setCacheWhitelist({'templateNameOrPath': maxCaches}): Establish a whitelist of templates to cache and set their maxCache value.
    • Example: {'one.html': 1, 'two.html': 50, 'three.html': 250}.
    • The above example will only allow caching on one.html, two.html. and three.html. No other template renders will be cached.
    • Also one.html will have a maximum unique cache count of 1, two.html's maximum will be 50, and three.html's maximum will be 250.
    • Note: mutually exclusive with teddy.setCacheBlacklist
  • teddy.setCacheBlacklist(templateArray): Establish a blacklist of templates to never cache.
    • Example: ['one.html', 'two.html', 'three.html'].
    • Note: mutually exclusive with teddy.setCacheWhitelist.
  • teddy.setDefaultParams(): Reset all params to default.
  • teddy.flushCache(template): Delete all the caches of a given template by supplying either its source code or a file name (in Node.js).
  • teddy.flushCache(template, model): Delete the cache of a specific template and model combination by supplying the template's source code or file name (in Node.js) along with the desired model to match.
  • teddy.maxPasses(n): Sets the maximum number of passes the parser can execute over your template. If this maximum is exceeded, Teddy will stop attempting to render the template. The limit exists to prevent the possibility of teddy producing infinite loops due to improperly coded templates.
    • Default: 25000.
  • teddy.compileAtEveryRender(true/false): When this setting is enabled, Teddy will compile the template at each render rather than caching previous compiles.
    • Default is false. (Not recommended to enable in production for performance reasons.)
  • teddy.minify(true/false): When this setting is enabled, Teddy will minify templates using its own internal minifier during the compile step.
    • Default is false. (Not recommended. Usually best to use a third party tool like html-minifier instead.)

Client-side browser support

Teddy is supported on all modern browsers.

Teddy is also supported in Internet Explorer 9+. Teddy may work in earlier versions of IE too but that isn't easy to test because the mocha/chai unit tests do not work in IE8 and below.

How to run the unit tests

Want to hack teddy's code but don't want to break something and cause a regression in the process? Run the supplied unit tests to sanity check existing features.

Start by cloning the git repo:

git clone
cd teddy

Install dependencies for the tests:

npm i

Run tests:

npm test

The default npm test command runs the tests server-side in Node.js and client-side in Chrome. See below commands for other browsers:

npm run test-firefox
npm run test-ie
npm run test-safari