JavaScript DHTML/Page Components/Table Of Content

Create a table of contents(TOC) for this document

/*
Examples From
JavaScript: The Definitive Guide, Fourth Edition
Legal matters: these files were created by David Flanagan, and are
Copyright (c) 2001 by David Flanagan.  You may use, study, modify, and
distribute them for any purpose.  Please note that these examples are
provided "as-is" and come with no warranty of any kind.
David Flanagan
*/
/**
 * Create a table of contents for this document, and insert the TOC into
 * the document by replacing the node specified by the replace argument.
 **/
function maketoc(replace) {
    // Create a <div> element that is the root of the TOC tree
    var toc = document.createElement("div");
    // Set a background color and font for the TOC.  We"ll learn about
    // the style property in the next chapter
    toc.style.backgroundColor = "white";
    toc.style.fontFamily = "sans-serif";
    // Start the TOC with an anchor so we can link back to it.
    var anchor = document.createElement("a");  // Create an <a> node
    anchor.setAttribute("name", "TOC");        // Give it a name
    toc.appendChild(anchor);                   // And insert it
    // Make the body of the anchor the title of the TOC
    anchor.appendChild(document.createTextNode("Table Of Contents"));
    // Create a <table> element that will hold the TOC and add it 
    var table = document.createElement("table");
    toc.appendChild(table);
    // Create a <tbody> element that holds the rows of the TOC
    var tbody = document.createElement("tbody");
    table.appendChild(tbody);
    // Initialize an array that keeps track of section numbers
    var sectionNumbers = [0,0,0,0,0,0];
    // Recursively traverse the body of the document, looking for sections
    // marked with <h1>, <h2>, ... tags, and use them to create the TOC
    // by adding rows to the table.
    addSections(document.body, tbody, sectionNumbers);
    // Finally, insert the TOC into the document by replacing the node
    // specified by the replace argument with the TOC sub-tree
    replace.parentNode.replaceChild(toc, replace);
    // This method recursively traverses the tree rooted at node n, looking
    // for <h1> through <h6> tags and uses the content of these tags to build
    // the table of contents by adding rows to the HTML table specified by the
    // toc argument.  It uses the sectionNumbers array to keep track of the
    // current section number.
    // This function is defined inside of maketoc() so that it is not
    // visible from the outside.  maketoc() is the only function
    // exported by this JavaScript module.
    function addSections(n, toc, sectionNumbers) {
        // Loop through all the children of n
        for(var m = n.firstChild; m != null; m = m.nextSibling) {
      // Check whether m is a heading element.  It would be nice if we
            // could just use (m instanceof HTMLHeadingElement), but this is
            // not required by the specification and it does not work in IE.
            // Therefore we"ve got to check the tagname to see if it is H1-H6.
            if ((m.nodeType == 1) &&  /* Node.ELEMENT_NODE */ 
                (m.tagName.length == 2) && (m.tagName.charAt(0) == "H")) {
    // Figure out what level heading it is
                var level = parseInt(m.tagName.charAt(1));
                if (!isNaN(level) && (level >= 1) && (level <= 6)) {
        // Increment the section number for this heading level
        sectionNumbers[level-1]++;
        // And reset all lower heading level numbers to zero
        for(var i = level; i < 6; i++) sectionNumbers[i] = 0;
        // Now combine section numbers for all heading levels
        // to produce a section number like 2.3.1
        var sectionNumber = "";
        for(var i = 0; i < level; i++) {
      sectionNumber += sectionNumbers[i];
      if (i < level-1) sectionNumber += ".";
        }
        // Create an anchor to mark the beginning of this section.
        // This will be the target of a link we add to the TOC.
        var anchor = document.createElement("a");
        anchor.setAttribute("name", "SECT"+sectionNumber);
        // Create a link back to the TOC and make it a
        // child of the anchor
        var backlink = document.createElement("a");
        backlink.setAttribute("href", "#TOC");
        backlink.appendChild(document.createTextNode("Contents"));
        anchor.appendChild(backlink);
        // Insert the anchor into the document right before the
        // section header
        n.insertBefore(anchor, m);
        // Now create a link to this section.  It will be added
        // to the TOC below.
        var link = document.createElement("a");
        link.setAttribute("href", "#SECT" + sectionNumber);
        // Get the heading text using a function defined below
        var sectionTitle = getTextContent(m);
        // Use the heading text as the content of the link.
        link.appendChild(document.createTextNode(sectionTitle));
        // Create a new row for the TOC
        var row = document.createElement("tr");
        // Create two columns for the row
        var col1 = document.createElement("td");
        var col2 = document.createElement("td");
        // Make the first column right-aligned and put the section
        // number in it
        col1.setAttribute("align", "right");
        col1.appendChild(document.createTextNode(sectionNumber));
        // Put a link to the section in the second column
        col2.appendChild(link);
        // Add the columns to the row, and the row to the table
        row.appendChild(col1);
        row.appendChild(col2);
        toc.appendChild(row);
        // Modify the section header element itself to add
        // the section number as part of the section title
        m.insertBefore(document.createTextNode(sectionNumber+": "),
           m.firstChild);
                }
            }
      else { // Otherwise, this is not a heading element, so recurse
    addSections(m, toc, sectionNumbers);
      }
        }
    }
    // This utility function traverses the node n, returning the content of
    // all text nodes found, and discarding any HTML tags.  This is also
    // defined as a nested function so that it is private to this module.
    function getTextContent(n) {
        var s = "";
        var children = n.childNodes;
        for(var i = 0; i < children.length; i++) {
            var child = children[i];
            if (child.nodeType == 3 /*Node.TEXT_NODE*/) s += child.data;
            else s += getTextContent(child);
        }
        return s;
    }
}