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Fragment

Fragment is a Javascript DSL for assembling HTML documents from living DOM nodes.

Why?

  1. Because programming with live references to DOM nodes is lighter, simpler, and cleaner than any other way of creating two-way bindings in the browser. Nobody should have to live with this: http://colynb.com/posts/dom-horror-with-emberjs.html

  2. Because when you have a deep hierarchy of views and subviews with lots of complex events and they need to be dynamically added and removed from the DOM frequently (ie - if you're building a one-page app), you're going to eventually run into a lot of mess that comes from keeping the hierarchy of subviews straight.

When your template is made of real DOM Elements, your life is better.

Overview

Unlike most templating systems, Fragment does not generate strings of HTML. Instead, Fragment returns a DocumentFragment object, containing a tree of elements generated in javascript. These elements are in-memory objects which means they can already have events bound on them.

Fragment will evaluate variables or functions passed to a template, meaning you can create view objects that return DOM nodes, and call them directly in the template.

Usage

Include fragment.js in your project, create a template, and call Fragment.parse on it.

It's a little nicer using Coffeescript, which has easier support for multi-line strings:

template = """
.wrapper
  p I'm just a paragraph
  p = @variable
  p == @node()
"""

fragment = Fragment.parse template,
  variable: "I'm a variable!"
  node: ->
    b = document.createElement('button')
    b.innerText = "Click me!"
    b.addEventListener 'click', ->
      console.log "You clicked the button!"
    b

document.body.appendChild(fragment)

Syntax

Fragment uses a terse syntax similar to Slim (and Jade and Haml). However, it is very minimal and completely logic-less.

Elements are defined with strings like this:

<selector>{<attributes>} <directive> <content>

Selectors

You can define elements using CSS selectors. IE:

p Content -> <p>Content</p>
p.example Hello World -> <p class="example">Hello World</p>
.text I'm a div -> <div class="text">I'm a div</div>
#myID I've got an ID -> <div id="myID">I've got an ID</div>

Attributes

You can pass a javascript object after a selector and it will be evalulated and turned into attributes. For example:

h1{data-state:"awesome"} Awesome Headline! -> <h1 data-state="awesome">Awesome Headline!</h1>

Directives and Content

There are four directives available:

  • | creates a text node
  • ' creates a text node with trailing whitespace
  • = evaluates a property or function, expecting a string
  • == evaluates a property or function, expecting a DOMElement

Indentation

Fragment is whitespace-sensitive, like Slim, Haml, Jade, and expects you to use two spaces to nest content. Note that you can either include content inline (beside a selector) or nested under it, but not both.

Miscelaneous

When you insert a node into a template you're placing the actual in-memory object into a document fragment. You can only place a reference to a node in a single place, if you refer to it a second time it will get moved to the second location. If you want to place multiple copies of DOM nodes you'll need to clone them first.