有一段javascript脚本，想添加一个功能

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function outputFolderLink()
{
  if (this.hreference)
  {
    doc.write("<a href='#' onClick='javascript:MyGotoPage(" + this.hreference + "); return false'")
    if (browserVersion > 0)
      doc.write("onClick='javascript:clickOnFolder("+this.id+")'")
    doc.write(">")
  }
  else
    doc.write("<a>")
}

function addChild(childNode)
{
  this.children[this.nChildren] = childNode
  this.nChildren++
  return childNode
}

function folderSubEntries()
{
  var i = 0
  var se = this.nChildren

  for (i=0; i < this.nChildren; i++){
    if (this.children[i].children)
      se = se + this.children[i].subEntries()
  }

  return se
}

function Item(itemDescription, itemLink)
{
  this.desc = itemDescription
  this.link = itemLink
  this.id = -1
  this.navObj = 0
  this.iconImg = 0
  this.iconSrc = "images/pg_bdoc.gif"

  this.initialize = initializeItem
  this.createIndex = createEntryIndex
  this.hide = hideItem
  this.display = display
  this.renderOb = drawItem
  this.totalHeight = totalHeight
}

function hideItem()
{
  if (browserVersion == 1) {
    if (this.navObj.style.display == "none")
      return
    this.navObj.style.display = "none"
  } else {
    if (this.navObj.visibility == "hiden")
      return
    this.navObj.visibility = "hiden"
  }
}

function initializeItem(level, lastNode, leftSide)
{
  this.createIndex()

  if (level>0)
    if (lastNode)
    {
      this.renderOb(leftSide + "<img src='images/pg_blastnode.gif' width=16 height=22>")
      leftSide = leftSide + "<img src='images/pg_bblank.gif' width=16 height=22>"
    }
    else
    {
      this.renderOb(leftSide + "<img src='images/pg_bnode.gif' width=16 height=22>")
      leftSide = leftSide + "<img src='images/pg_bvertline.gif' width=16 height=22>"
    }
  else
    this.renderOb("")
}

function drawItem(leftSide)
{
  if (browserVersion == 2)
    doc.write("<layer id='item" + this.id + "' top=" + doc.yPos + " visibility=hiden>")

  doc.write("<table class='toolbar' ")
  if (browserVersion == 1)
    doc.write(" id='item" + this.id + "' style='position:block;' ")
  doc.write(" border=0 cellspacing=0 cellpadding=0>")
  doc.write("<tr><td>")
  doc.write(leftSide)
  doc.write("<a href=" + this.link + ">")
  doc.write("<img id='itemIcon"+this.id+"' ")
  doc.write("src='"+this.iconSrc+"' border=0>")
doc.write("</a>")
  doc.write("</td><td valign=middle nowrap>")
  if (USETEXTLINKS)
    doc.write("<a href=" + this.link + ">" + this.desc + "</a>")
  else
    doc.write(this.desc)
  doc.write("</table>")

  if (browserVersion == 2)
    doc.write("</layer>")

  if (browserVersion == 1) {
    this.navObj = doc.all["item"+this.id]
    this.iconImg = doc.all["itemIcon"+this.id]
  } else if (browserVersion == 2) {
    this.navObj = doc.layers["item"+this.id]
    this.iconImg = this.navObj.document.images["itemIcon"+this.id]
    doc.yPos=doc.yPos+this.navObj.clip.height
  }
}

function display()
{
  if (browserVersion == 1)
    this.navObj.style.display = "block"
  else
    this.navObj.visibility = "show"
}

function createEntryIndex()
{
  this.id = nEntries
  indexOfEntries[nEntries] = this
  nEntries++
} function totalHeight()
{
  var h = this.navObj.clip.height
  var i = 0

  if (this.isOpen)
    for (i=0 ; i < this.nChildren; i++)
      h = h + this.children[i].totalHeight()

  return h
} function clickOnFolder(folderId)
{
var clicked = indexOfEntries[folderId]

  if (!clicked.isOpen)
    clickOnNode(folderId)

  return

  if (clicked.isSelected)
    return
} function clickOnNode(folderId)
{
  var clickedFolder = 0
  var state = 0

  clickedFolder = indexOfEntries[folderId]
  state = clickedFolder.isOpen

  clickedFolder.setState(!state)
}
function initializeDocument()
{
  if (doc.all)
    browserVersion = 1
  else
    if (doc.layers)
      browserVersion = 2
    else
      browserVersion = 0

  root0.initialize(0, 1, "")
  root0.display()

  if (browserVersion > 0)
  {
    doc.write("<layer top="+indexOfEntries[nEntries-1].navObj.top+"> </layer>")

    clickOnNode(0)     clickOnNode(0)
  }
}

function gFld(description, hreference)
{
  folder = new Folder(description, hreference)
  return folder
} function gLnk(target, description, linkData)
{
  fullLink = ""

  if (target==0)
  {
    fullLink = "'"+linkData+"' target=\"basefrm\""
  }
  else
  {
fullLink = "'#' onClick='javascript:MyGotoPage(" + linkData + "); return false'"
  }
  linkItem = new Item(description, fullLink)
  return linkItem
} function insFld(parentFolder, childFolder)
{
  parentFolder.setStateFolder  return parentFolder.addChild(childFolder)
}

function insDoc(parentFolder, document)
{
parentFolder.setStateFolder
  parentFolder.addChild(document)
}

USETEXTLINKS = 1
indexOfEntries = new Array
nEntries = 0
doc = document
browserVersion = 0
selectedFolder=0</script>
<script>
root0 = gFld("c++", "")
root1 = insFld(root0, gFld("More Effective C++ [Meyers96]", "1"))
insDoc(root1, gLnk(2,"Dedication", "3"))
insDoc(root1, gLnk(2,"Acknowledgments", "4"))
insDoc(root1, gLnk(2,"Introduction", "7"))
root2 = insFld(root1, gFld("Basics", "12"))
insDoc(root2, gLnk(2,"Item 1: Distinguish between pointers and references.", "13"))
insDoc(root2, gLnk(2,"Item 2: Prefer C++-style casts.", "15"))
insDoc(root2, gLnk(2,"Item 3: Never treat arrays polymorphically.", "19"))
insDoc(root2, gLnk(2,"Item 4: Avoid gratuitous default constructors.", "21"))
root2 = insFld(root1, gFld("Operators", "25"))
insDoc(root2, gLnk(2,"Item 5: Be wary of user-defined conversion functions.", "26"))
insDoc(root2, gLnk(2,"Item 6: Distinguish between prefix and postfix forms of increment and decrement operators.", "31"))
insDoc(root2, gLnk(2,"Item 7: Never overload &&, ||, or ,.", "34"))
insDoc(root2, gLnk(2,"Item 8: Understand the different meanings of new and delete.", "37"))
root2 = insFld(root1, gFld("Exceptions", "42"))
insDoc(root2, gLnk(2,"Item 9: Use destructors to prevent resource leaks.", "43"))
insDoc(root2, gLnk(2,"Item 10: Prevent resource leaks in constructors.", "47"))
insDoc(root2, gLnk(2,"Item 11: Prevent exceptions from leaving destructors.", "53"))
insDoc(root2, gLnk(2,"Item 12: Understand how throwing an exception differs from passing a parameter or calling a virtual function.", "55"))
insDoc(root2, gLnk(2,"Item 13: Catch exceptions by reference.", "61"))
insDoc(root2, gLnk(2,"Item 14: Use exception specifications judiciously.", "64"))
insDoc(root2, gLnk(2,"Item 15: Understand the costs of exception handling.", "69"))
root2 = insFld(root1, gFld("Efficiency", "71"))
insDoc(root2, gLnk(2,"Item 16: Remember the 80-20 rule.", "72"))
insDoc(root2, gLnk(2,"Item 17: Consider using lazy evaluation.", "74"))
insDoc(root2, gLnk(2,"Item 18: Amortize the cost of expected computations.", "80"))
insDoc(root2, gLnk(2,"Item 19: Understand the origin of temporary objects.", "84"))
insDoc(root2, gLnk(2,"Item 20: Facilitate the return value optimization.", "86"))
insDoc(root2, gLnk(2,"Item 21: Overload to avoid implicit type conversions.", "89"))
insDoc(root2, gLnk(2,"Item 22: Consider using op= instead of stand-alone op.", "91"))
insDoc(root2, gLnk(2,"Item 23: Consider alternative libraries.", "94"))
insDoc(root2, gLnk(2,"Item 24: Understand the costs of virtual functions, multiple inheritance, virtual base classes, and RTTI.", "96"))
root2 = insFld(root1, gFld("Techniques", "103"))
insDoc(root2, gLnk(2,"Item 25: Virtualizing constructors and non-member functions.", "104"))
insDoc(root2, gLnk(2,"Item 26: Limiting the number of objects of a class.", "109"))
insDoc(root2, gLnk(2,"Item 27: Requiring or prohibiting heap-based objects.", "120"))
insDoc(root2, gLnk(2,"Item 28: Smart pointers.", "130"))
insDoc(root2, gLnk(2,"Item 29: Reference counting.", "147"))
insDoc(root2, gLnk(2,"Item 30: Proxy classes.", "170"))
insDoc(root2, gLnk(2,"Item 31: Making functions virtual with respect to more than one object.", "181"))
root2 = insFld(root1, gFld("Miscellany", "198"))
insDoc(root2, gLnk(2,"Item 32: Program in the future tense.", "199"))
insDoc(root2, gLnk(2,"Item 33: Make non-leaf classes abstract.", "203"))
insDoc(root2, gLnk(2,"Item 34: Understand how to combine C++ and C in the same program.", "212"))
insDoc(root2, gLnk(2,"Item 35: Familiarize yourself with the language standard .", "217"))
insDoc(root1, gLnk(2,"Recommended Reading", "222"))
insDoc(root1, gLnk(2,"An auto_ptr Implementation", "226"))
insDoc(root1, gLnk(2,"Books' Index", "229"))
</script><script>initializeDocument()</script></head>
<body bgcolor=white  style="border-right: 2 solid #CCCCCC">
</body>