path: root/js/README.mkd

Luigi Template
==============

Overview
--------
Tiny JavaScript string templating library.

Features
--------

* Filters, with common filters built-in.
* Template caching.
* Small: Less than 4k minified (see `luigi-template.min.js`),
* Stand-alone: No external dependencies (no jQuery, etc),
* Compatible: Works in browsers as old as IE9
* MIT-licensed

Usage
-----
A minimal template:

    // create template
    var t = new LuigiTemplate('hello %{name}');

    // run template, print result to console
    console.log(t.run({
      name: 'Paul',
    }));

    // prints "hello Paul"

If you have a template that you only need to run one time, you can use
the `LuigiTemplate.run()` singleton to run it, like this:

    // create and run template in one shot
    var r = LuigiTemplate.run('hello %{name}', {
      name: 'Paul',
    });

    // print result to console
    console.log(r);

    // prints "hello Paul"

Templates parameters can be modified by filters.  Filters are applied to
a parameter value by appending a `|` (pipe) character, followed by the
filter name.

Here is the template from above, with the name value HTML-escaped using
a built-in filter:

    // create template that prints hello and the HTML-escaped name
    var t = new LuigiTemplate('hello %{name | h}');

    // run template, print result to console
    console.log(t.run({
      name: '<Paul>',
    }));

    // prints "hello &lt;Paul&gt;"

The built-in templates are:

* `uc`: Upper-case string.
* `lc`: Lower-case string.
* `s`: Returns `""` if the value is 1, and `"s"` otherwise. Used to
  pluralize values.  Example:

    console.log(LuigiTemplate.run('a: a%{a|s}, b: b%{b|s}, c: c%{c|s}'', {
      a: 0,
      b: 1,
      c: 2,
    }));

    // prints "a: as, b: b, c: cs"

* `length`: Get the length of an array.
* `trim`: Trim leading and trailing whitespace from a string.
* `h`: HTML-escape a string value.
* `u`: URL-escape a string value.
* `json`: JSON-encode a value.

You can create your own custom filters, too.

The easiest way to create your own custom filter is to add it to the set
of global filters (`LuigiTemplate.FILTERS`), like so:

    // add global template filter
    LuigiTemplate.FILTERS.barify = function(s) {
      return 'bar-' + s + '-bar';
    };

    // create template that uses custom global filter
    var t = new LuigiTemplate('hello %{name | barify | h}');

    // run template, print result to console
    console.log(t.run({
      name: '<Paul>',
    }));

    // prints "hello bar-&lt;Paul&gt;-bar"

You can also create a custom filters and limit it to a particular
template by passing a hash as the second parameter to the
`LuigiTemplate` constructor, like this:

    // create template with custom template-specific filter
    var t = new LuigiTemplate('hello %{name | barify | h}', {
      barify: function(s) {
        return 'bar-' + s + '-bar';
      },
    });

    // run template, print result to console
    console.log(t.run({
      name: '<Paul>',
    }));

    // prints "hello bar-&lt;Paul&gt;-bar"

You can pass arguments to your custom filters as well.  Here's an
example:

    // create template with custom template-specific filter named
    // "wrap", which wraps the value in the given filter parameters
    var t = new LuigiTemplate('hello %{name | wrap head tail | h}', {
      wrap: function(s, args) {
        if (args.length == 2) {
          return [args[0], s, args[1]].join('-';
        } else if (args.length == 1) {
          return [args[0], s, args[0]].join('-');
        } else {
          return s;
        }
      },
    });

    // run template, print result to console
    console.log(t.run({
      name: '<Paul>',
    }));

    // prints "hello head-&lt;Paul&gt;-tail"

If you have a lot of separate templates, or a few large templates,
then it's a good idea to use a template cache.

A template cache will create templates as they are needed (also known as
"lazy initialization"), so the page or application loads quickly.  A
template cache also caches instantiated (that is, created) templates for
future use, so using templates from the cache is fast, too.

Finally, template caches serve as a good repository for all of the
templates in a script.

Here's how you create a template cache:

    // create template cache with a single template
    var cache = LuigiTemplate.cache({
      hello: 'hello %{name | uc | h}'
    });

    // run template, print result to console
    console.log(cache.run('hello', {
      name: '<Paul>',
    }));

    // prints "hello &lt;PAUL%gt;"

Documentation
-------------
*TODO*

Tests
-----
This `test/` directory contains the JavaScript test suite for the
JavaScript implementation of [Luigi Template][], written in [Mocha][]
and [Chai].

To run the test suite, load `test/test.html` in a browser.

Author
------
Paul Duncan ([pabs@pablotron.org][me])<br/>
https://pablotron.org/

License
-------
Copyright 2014-2018 Paul Duncan ([pabs@pablotron.org][me])

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

[Luigi Template]: https://github.com/pablotron/luigi-template
[me]: mailto:pabs@pablotron.org
[Mocha]: https://mochajs.org/
[Chai]: http://www.chaijs.com/