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JavaScript Tree Control

Maintainers

Sam Minnee (sam at silverstripe dot com)

Features

Build trees using semantic HTML and unobtrusive JavaScript.
Style the tree to suit your application you with CSS.
Demo: http://www.silverstripe.org/assets/tree/demo.html

Usage

The first thing to do is include the appropriate JavaScript and CSS files:

<code html>
<link rel="stylesheet" type="text/css" media="all" href="tree.css" />
<script type="application/javascript" src="tree.js"></script>
</code>

Then, create the HTML for you tree. This is basically a nested set of bullet pointed links. The "tree" class at the top is what the script will look for. Note that you can make a tree node closed to begin with by adding class="closed".

Here's the HTML code that I inserted to create the demo tree above.

<code html>
<ul class="tree">
  <li><a href="#">item 1</a>
    <ul>
      <li><a href="#">item 1.1</a></li>
      <li class="closed"><a href="#">item 1.2</a>
        <ul>
          <li><a href="#">item 1.2.1</a></li>
          <li><a href="#">item 1.2.2</a></li>
          <li><a href="#">item 1.2.3</a></li>
        </ul>
      </li>
      <li><a href="#">item 1.3</a></li>
    </ul>
  </li>
  <li><a href="#">item 2</a>
    <ul>
      <li><a href="#">item 2.1</a></li>
      <li><a href="#">item 2.2</a></li>
      <li><a href="#">item 2.3</a></li>
    </ul>	
  </li>
</ul> 	 	 	
</code>

Your tree is now complete!

How it works

Obviously, this isn't a complete detail of everything that's going on, but it gives you an insight into the overall process.

Starting the script

In simple situations, creating an auto-loading script is a simple matter of setting window.onload to a function. But what if there's more than one script? To this end, we created an appendLoader() function that will execute multiple loader functions, including a previously defined loader function

Finding the tree content

Rather than write a piece of script to define where your tree is, we've tried to make the script as automatic as possible - it finds all ULs with a class name containing "tree".

Augmenting the HTML

Unfortunately, an LI containing an A isn't sufficient for doing all of the necessary tree styling. Rather than force people to put non-semantic HTML into their file, the script generates extra <span> tags.

So, the following HTML:

<code html>
<li>
  <a href="#">My item</a>
</li> 
</code>

Is turned into the more ungainly, and yet more easily styled:

<code html>
<li>
  <span class="a"><span class="b"><span class="c">
        <a href="#">My item</a>
  </span></span></span>
</li> 
</code>

Additionally, some helper classes are applied to the <li> and <span class="a"> elements:

"last" is applied to the last node of any subtree.
"children" is applied to any node that has children.

Styling it up

Why the heck do we need 5 styling elements? Basically, because there are 5 background-images to apply:

li: A repeating vertical line is shown. Nested
tags give us the multiple vertical lines that we need.
span.a: We overlay the vertical line with 'L' and 'T' elements as needed.
span.b: We overlay '+' or '-' signs on nodes with children.
span.c: This is needed to fix up the vertical line.
a: Finally, we apply the page icon.

Opening / closing nodes

Having come this far, the "dynamic" aspect of the tree control is very trivial. We set a "closed" class on the <li> and <span class="a"> elements, and our CSS takes care of hiding the children, changing the - to a + and changing the folder icon.

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