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Making An Interactive TreeView Control From An HTML Nested List

Create a list, give it an ID, and set this event handler on the list.

By V. Subhash

I was preparing for a presentation and I did not want use PowerPoint. The presentation was about HTML. So, what better way to demonstrate HTML than using it as the PowerPoint replacement. Here is what I did.

First, I created a nested HTML list and gave it an ID.

<ul id="LinkedList1" class="LinkedList">
  <li>History of WWW
    <ul>
      <li>Arpanet - Packets - 1969</li>
      <li>TCP/IP - Vinton Cerf - 1974</li>
      <li>WorldWideWeb (Internet and program) - Tim Berners Lee - 1991</li>
…

Then, I added this style so that the list tree is collapsed by default.

<style type="text/css">
  ul.LinkedList { display: block; }
  ul.LinkedList ul { display: none; } 
  .HandCursorStyle { cursor: pointer; cursor: hand; }  /* For IE */
</style>

If you want the list to be expanded by default, say for JavaScript-disabled clients, then you can comment out the second-line.

<style type="text/css">
  ul.LinkedList { display: block; }
  /* ul.LinkedList ul { display: none; } */
  .HandCursorStyle { cursor: pointer; cursor: hand; }  /* For IE */
</style>

Then, I add the click event handler.

  <script type="text/JavaScript">
    // Add this to the onload event of the BODY element
    function addEvents() {
      activateTree(document.getElementById("LinkedList1"));
    }

    // This function traverses the list and add links 
    // to nested list items
    function activateTree(oList) {
      // Collapse the tree
      for (var i=0; i < oList.getElementsByTagName("ul").length; i++) {
        oList.getElementsByTagName("ul")[i].style.display="none";            
      }                                                                  
      // Add the click-event handler to the list items
      if (oList.addEventListener) {
        oList.addEventListener("click", toggleBranch, false);
      } else if (oList.attachEvent) { // For IE
        oList.attachEvent("onclick", toggleBranch);
      }
      // Make the nested items look like links
      addLinksToBranches(oList);
    }

    // This is the click-event handler
    function toggleBranch(event) {
      var oBranch, cSubBranches;
      if (event.target) {
        oBranch = event.target;
      } else if (event.srcElement) { // For IE
        oBranch = event.srcElement;
      }
      cSubBranches = oBranch.getElementsByTagName("ul");
      if (cSubBranches.length > 0) {
        if (cSubBranches[0].style.display == "block") {
          cSubBranches[0].style.display = "none";
        } else {
          cSubBranches[0].style.display = "block";
        }
      }
    }

    // This function makes nested list items look like links
    function addLinksToBranches(oList) {
      var cBranches = oList.getElementsByTagName("li");
      var i, n, cSubBranches;
      if (cBranches.length > 0) {
        for (i=0, n = cBranches.length; i < n; i++) {
          cSubBranches = cBranches[i].getElementsByTagName("ul");
          if (cSubBranches.length > 0) {
            addLinksToBranches(cSubBranches[0]);
            cBranches[i].className = "HandCursorStyle";
            cBranches[i].style.color = "blue";
            cSubBranches[0].style.color = "black";
            cSubBranches[0].style.cursor = "auto";
          }
        }
      }
    }
  </script>
</head>
<body onload="addEvents();">

Demo (Click The Faux Links In The List)

Here is how it works. The blue-colored text are not hyperlinks. They hide nested branches. Click the blue-colored text to expand the hidden branches.

History of WWW
- Arpanet - Packets - 1969
- TCP/IP - Vinton Cerf - 1974
- WorldWideWeb (Internet and program) - Tim Berners Lee - 1991
- Public Domain WWW source code - 1993
- NCSA Mosaic released - 1993
- Opera released - 1994
- Marc Anderseen (formerly NCSA) and Jim Clark release Netscape - 1994
- IE from Microsoft (based on Mosaic)
  - DHTML
  - ActiveX
- W3C at MIT (CERN, NCSA, EU)
- W3C Recommendations
- Mozilla Foundation
HTML4 page structure
- Comments
- Tags
  - Head
    - title
    - meta
    - link
    - script
  - Body
    - inline tags - b (bold), i (italic), ~~s (strikeout)~~, u (underline), code (fixed-width), span, a (anchor - hyperlink)
    - block tags - div (box), table/tr/td (table), ul/ol/li (list)
    - other tags - script, noscript
- JavaScript
  - IE (see MSDN)
  - Mozilla (see MDC)
  - Ajax
- CSS2
  - Mozilla (see W3C reference)
  - IE (see MSDN for filter style)
  - Accessibility
Doctype - HTML (Transitional/Strict) or XHTML
How Web Pages Work
- HTTP request
- HTTP response
Web Applications - Server-side scripting
- CGI
- ASP, JSP, PHP
- ASP.NET
Browser engines
- IE
- Mozilla
- KHTML/Webkit
Mobile browsers
- WAP - very old phones
- XHTML - cheap phones
- HTML, XHTML, HTML5 - new/expensive phones
HTML 5 and CSS3 - What's New

Example HTML Source

Here is the test page source code. It has been tested OK in IE (v5.5 to v9 Beta) and recent versions of (Google Chrome-based) Comodo Dragon, Firefox and Opera.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8" />
  <title>HTML Course</title>

// This function traverses the list and add links 
    // to nested list items
    function activateTree(oList) {
      // Collapse the tree
      for (var i=0; i < oList.getElementsByTagName("ul").length; i++) {
        oList.getElementsByTagName("ul")[i].style.display="none";            
      }                                                                  
      // Add the click-event handler to the list items
      if (oList.addEventListener) {
        oList.addEventListener("click", toggleBranch, false);
      } else if (oList.attachEvent) { // For IE
        oList.attachEvent("onclick", toggleBranch);
      }
      // Make the nested items look like links
      addLinksToBranches(oList);
    }

// This is the click-event handler
    function toggleBranch(event) {
      var oBranch, cSubBranches;
      if (event.target) {
        oBranch = event.target;
      } else if (event.srcElement) { // For IE
        oBranch = event.srcElement;
      }
      cSubBranches = oBranch.getElementsByTagName("ul");
      if (cSubBranches.length > 0) {
        if (cSubBranches[0].style.display == "block") {
          cSubBranches[0].style.display = "none";
        } else {
          cSubBranches[0].style.display = "block";
        }
      }
    }

// This function makes nested list items look like links
    function addLinksToBranches(oList) {
      var cBranches = oList.getElementsByTagName("li");
      var i, n, cSubBranches;
      if (cBranches.length > 0) {
        for (i=0, n = cBranches.length; i < n; i++) {
          cSubBranches = cBranches[i].getElementsByTagName("ul");
          if (cSubBranches.length > 0) {
            addLinksToBranches(cSubBranches[0]);
            cBranches[i].className = "HandCursorStyle";
            cBranches[i].style.color = "blue";
            cSubBranches[0].style.color = "black";
            cSubBranches[0].style.cursor = "auto";
          }
        }
      }
    }
  </script>
</head>

<body onload="addEvents();">
<ul id="LinkedList1" class="LinkedList">
  <li>History of WWW
    <ul>
      <li>Arpanet - Packets - 1969</li>
      <li>TCP/IP - Vinton Cerf - 1974</li>
      <li>WorldWideWeb (Internet and program) - Tim Berners Lee - 1991</li>
      <li>Public Domain WWW source code - 1993</li>
      <li>NCSA Mosaic released - 1993</li>
      <li>Opera released - 1994</li>
      <li>Marc Anderseen (formerly NCSA) and Jim Clark  release Netscape - 1994</li>
      <li>IE from Microsoft (based on Mosaic)
        <ul>
          <li>DHTML</li>
          <li>ActiveX</li>
        </ul>
      </li>
      <li>W3C at MIT (CERN, NCSA, EU)</li>
      <li>W3C Recommendations</li>
      <li>Mozilla Foundation</li>
    </ul>
  </li>
  <li>HTML4 page structure
    <ul>
      <li>Comments</li>
      <li>Tags
        <ul> 
          <li>Head
            <ul>
              <li>title</li>
              <li>meta</li>
              <li>link</li>
              <li>script</li>
            </ul> 
          </li>
          <li>Body
            <ul>
              <li>inline tags - <b>b (bold)</b>, <i>i (italic)</i>, <s>s (strikeout)</s>,
                <u>u (underline)</u>, <code>code (fixed-width)</code>, 
                <span style="background-color: lime; ">span</span>, 
                <a href="http://www.gnostice.com/">a (anchor - hyperlink)</a></li>
              <li>block tags - div (box), table/tr/td (table), ul/ol/li (list)</li>
              <li>other tags - script, noscript</li>
            </ul>
          </li>
        </ul>
      </li>
      <li>JavaScript
        <ul>
          <li>IE (see MSDN)</li>
          <li>Mozilla (see MDC)</li>
          <li>Ajax</li>
        </ul>
      </li>
      <li>CSS2
        <ul>
          <li>Mozilla (see W3C reference)</li>
          <li>IE (see MSDN for filter style)</li>
          <li>Accessibility</li>
        </ul>
      </li>  
    </ul>
  </li>
  <li>Doctype - HTML (Transitional/Strict) or XHTML </li>
  <li>How Web Pages Work
    <ul>
      <li>HTTP request</li>
      <li>HTTP response</li>
    </ul>
  </li>    
  <li>Web Applications - Server-side scripting
     <ul>
       <li>CGI</li>
       <li>ASP, JSP, PHP</li>
       <li>ASP.NET</li>
     </ul>
  </li>
  <li>Browser engines
    <ul>
      <li>IE</li>
      <li>Mozilla</li>
      <li>KHTML/Webkit</li>
    </ul>
  </li>
  <li>Mobile browsers
    <ul>
      <li>WAP - very old phones</li>
      <li>XHTML - cheap phones</li>
      <li>HTML, XHTML, HTML5 - new/expensive phones</li>
    </ul>
  </li>
  <li>HTML 5 and CSS3 - What's New</li>
</ul>

</body>
</html>

---o0O0o---

Making An Interactive TreeView Control From An HTML Nested List

Create a list, give it an ID, and set this event handler on the list.

By V. Subhash

Demo (Click The Faux Links In The List)

Example HTML Source

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