thymeleafjs

ThymeleafJS
===========


A basic implementation of the Thymeleaf templating
engine in JavaScript.

Having worked with Thymeleaf for several years, other templating languages are
starting to look foreign to me. Upon evaluating several existing JavaScript
templating languages to help build a mock Node server for development, it made
me yearn for the natural templating feature of Thymeleaf.

This project aims first to perform similar tasks to existing JS templating
libraries like Mustache on Node servers
like Express. Once the Thymeleaf-in-JS dream is
achieved, I can start thinking about stretch goals to make it a better
companion to the original Thymeleaf for web development :)

Current goals
-------------

This project already works very well as a server-side template renderer, but now
I'm trying to get it to play nice with the original Thymeleaf, ie: render
templates on the server with Thymeleaf, then re-render the templates on the
client using ThymeleafJS with the same template code (I've been calling this
feature "isomorphic templating", akin to isomorphic JavaScript where the same
code is run on the client and server).

To help with this, I've written a simple TODO app in Spring Boot w/ Thymeleaf
and am using ThymeleafJS to test and develop this feature. The TODO app can be
found here: https://github.com/ultraq/thymeleafjs-todo

Natural Templates
-----------------

For those unfamiliar with Thymeleaf, it's main feature is being able to use
natural templates - HTML that can be correctly displayed in browsers and also
work as static prototypes, allowing for stronger collaboration in development
teams.

Borrowing the example from the front page of the Thymeleaf website:

``html


Hello (username)
You're using Thymeleaf for JavaScript! Wanna see some random fruit?

`
npm install thymeleaf --save
`


API
---

> thymeleafjs is still under development, denoted by the 0.x semver, so expect
> anything below to change.

Create a new instance of a Thymeleaf TemplateEngine, then use one of its
process* functions to process your Thymeleaf template, eg:

`javascript
import {TemplateEngine} from 'thymeleaf';

let templateEngine = new TemplateEngine();

// Render template from string
templateEngine.process('

// Render template from file
templateEngine.processFile('template.html', { greeting: 'Hello!' })
.then(result => {
// Do something with the result...
});
`

$3

The main class for the processing of templates.

#### new TemplateEngine(options)

When constructing a new instance of the template engine, a config object can be
passed in to set any of the available options. These are:

- dialects: array of Dialect instances to use in processing
- messageResolver: a function given a message key and optional message
parameters which should then return the message string or Promise of the
message string. Required if you want to use message expressions (#{...}).
- templateResolver: a function supplied the template name which should then
return the text or a Promise that will resolve with the text of the
template being requested. Required if you want to make use of template
fragment processors like th:insert.

`javascript
import {StandardDialect, TemplateEngine} from 'thymeleaf';

let templateEngine = new TemplateEngine({
dialects: [
new StandardDialect('th', { // Enable isomorphic mode with this config object
prefix: 'thjs'
})
],
messageResolver: (key, parameters) => {
// ...
},
templateResolver: templateName => {
// ...
}
});
`

#### process(templateString, context)

Process the Thymeleaf template, returning a Promise which is resolved with the
processed template.

- template: a Thymeleaf template string to process
- context: an object of key/value pairs, what the expressions evaluate to
and the values they're set to

#### processFile(templateFile, context)

Process the Thymeleaf template at the given file location, returning a Promise
which is resolved with the processed template.

- templateFile: path to the Thymeleaf template to process
- context: an object of key/value pairs, what the expressions evaluate to
and the values they're set to

$3

A basic class that is used as a template for implementing dialects that contain
processors and expression objects to expand Thymeleaf's functionality. The
Standard Dialect is itself an instance of Dialect.

To add processors, create a class that extends Dialect, and add either a
processors property or getter which is an array of processors.

To add expression objects, extend Dialect and add either a expressionObjects
property or getter which is an object whose keys are the expression object names
(starting with # as the convention from Thymeleaf) and the values are the
expression objects.

$3

A basic class that is used for creating processors that work using HTML
attributes.

$3

A processor for working on HTML elements.

$3

The built-in dialect that provides all the functionality that Thymeleaf is known
for. Importing this class is only useful for specifying a prefix different from
the default of thjs, eg:

`javascript
import {TemplateEngine, StandardDialect} from 'thymeleaf';

let templateEngine = new TemplateEngine({
dialects: [
new StandardDialect('th')
]
});
`

Use the STANDARD_CONFIGURATION export to do this more
succinctly.

$3

A configuration object used to set the prefix to the th that many of us will
be used to from the original Thymeleaf. It also enables the experimental
"isomorphic mode", in which ThymeleafJS can also process original Thymeleaf
processing instructions, unless a thjs one is specified for the same name, in
which case that will take precedence.

`javascript
import {TemplateEngine, STANDARD_CONFIGURATION} from 'thymeleaf';

let templateEngine = new TemplateEngine(STANDARD_CONFIGURATION);
``

Supported features (so far)
---------------------------

See here for supported processors: https://github.com/ultraq/thymeleafjs/issues/21

See here for supported expression syntaxes: https://github.com/ultraq/thymeleafjs/issues/20

See here for supported expression objects: https://github.com/ultraq/thymeleafjs/issues/31

Integration
-----------

$3

Integration with the Express server is its own module,
express-thymeleaf. Installation
and usage instructions are also in that project's readme.