Manipulating XML Data with JavaScript

Example 21-7 defines a function named makeTable() that uses both the XML and HTML DOMs to extract data from an XML document and insert that data into an HTML document in the form of a table. The function expects a JavaScript object literal argument that specifies which elements of the XML document contain table data and how that data should be arranged in the table.

Before looking at the code for makeTable() , let’s first consider a usage example. Example 21-6 shows a sample XML document that’s used here (and elsewhere throughout this chapter).

example 21-6. An XML datafile

<?xml version="1.0"?>
<contacts>
  <contact name="Able Baker"><email>able@example.com</email></contact>
  <contact name="Careful Dodger"><email>dodger@example.com </email></contact>
  <contact name="Eager Framer" personal="true"><email>framer@example.com </email></contact>
</contacts>

The following HTML fragment shows how the makeTable() function might be used with that XML data. Note that the schema object refers to tag and attribute names from this sample datafile:

  <script>
  // This function uses makeTable()
  function displayAddressBook() {
     var schema = {
         rowtag: "contact",
         columns: [
             { tagname: "@name", label: "Name" },
             { tagname: "email", label: "Address" }
         ]
     };

     var xmldoc = XML.load("addresses.xml");     // Read the XML data
     makeTable(xmldoc,
schema, "addresses");  // Convert to an HTML table
  }
  </script>

  <button onclick="displayAddressBook()">Display Address Book</button>
  <div id="addresses"><!--table will be inserted here --></div>

The implementation of makeTable() is shown in Example 21-7.

Example 21-7. Building an HTML table from XML data

/**
 * Extract data from the specified XML document and format it as an HTML table.
 * Append the table to the specified HTML element. (If element is a string,
 * it is taken as an element ID, and the named element is looked up.)
 *
 * The schema argument is a JavaScript object that specifies what data is to
 * be extracted and how it is to be displayed. The schema object must have a
 * property named "rowtag" that specifies the tag name of the XML elements that
 * contain the data for one row of the table. The schema object must also have
 * a property named "columns" that refers to an array. The elements of this
 * array specify the order and content of the columns of the table. Each
 * array element may be a string or a JavaScript object. If an element is a
 * string, that string is used as the tag name of the XML element that contains
 * table data for the column, and also as the column header for the column.
 * If an element of the columns[] array is an object, it must have one property
 *named "tagname" and one named "label". The tagname property is used to
 * extract data from the XML document and the label property is used as the
 * column header text. If the tagname begins with an @ character, it is
 * an attribute of the row element rather than a child of the row.
 */
function makeTable(xmldoc, schema, element) {
    // Create the <table> element
    var table = document.createElement("table");

    // Create the header row of <th> elements in a <tr> in a <thead>
    var thead = document.createElement("thead");
    var header = document.createElement("tr");
    for(var i = 0; i < schema.columns.length; i++) {
        var c = schema.columns[i];
        var label = (typeof c == "string")?c:c.label;
        var cell = document.createElement("th");
        cell.appendChild(document.createTextNode(label));
        header.appendChild(cell);
    }
    // Put the header into the table
    thead.appendChild(header);
    table.appendChild(thead);

    // The remaining rows of the table go in a <tbody>
    var tbody = document.createElement("tbody");
    table.appendChild(tbody);

    // Now get the elements that contain our data from the xml document
    var xmlrows = xmldoc.getElementsByTagName(schema.rowtag);

    // Loop through these elements. Each one contains a row of the table.
    for(var r=0; r < xmlrows.length; r++) {
        // This is the XML element that holds the data for the row
        var xmlrow = xmlrows[r];
        // Create an HTML element to display the data in the row
        var row = document.createElement("tr");

        // Loop through the columns specified by the schema object
        for(var c = 0; c < schema.columns.length; c++) {
            var sc = schema.columns[c];
            var tagname = (typeof sc == "string")?sc:sc.tagname;
            var celltext;
            if (tagname.charAt(0) == '@') {
                // If the tagname begins with '@', it is an attribute name
                celltext = xmlrow.getAttribute(tagname.substring(1));
            }
            else {
                // Find the XML element that holds the data for this column
                var xmlcell = xmlrow.getElementsByTagName(tagname)[0];
                // Assume that element has a text node as its first child
                var celltext = xmlcell.firstChild.data;
            }
            // Create the HTML element for this cell
            var cell = document.createElement("td");
            // Put the text data into the HTML cell
            cell.appendChild(document.createTextNode(celltext));
            // Add the cell to the row
            row.appendChild(cell);
        }

        // And add the row to the tbody of the table
        tbody.appendChild(row);
    }

    // Set an HTML attribute on the table element by setting a property.
    // Note that in XML we must use setAttribute() instead.
    table.frame = "border";

    // Now that we've created the HTML table, add it to the specified element.
    // If that element is a string, assume it is an element ID.
    if (typeof element == "string") element = document.getElementById(element);
    element.appendChild(table);
}