• Build trees using semantic HTML and unobtrusive JavaScript.
• Style the tree to suit your application you with CSS.

• We have a simple demo of the tree’s operation: http://www.silverstripe.org/assets/tree/demo.html
• Download the package: http://www.silverstripe.org/assets/tree/tree.zip - 11kb

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

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

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.

<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>

Your tree is now complete!

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

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

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”.

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:

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

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

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

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.

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 <li> 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.

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.

Like the rest of our open-source software, the SilverStripe Tree Control is released under the BSD License, which means that you can put it into both open-source and commercial projects.