Q1781 How to make a collapsible treeview applet with JavaScript?

//Example. Constructor of class folder:

function Folder(folderDescription, hreference) //constructor 
{ 
  //constant data 
  this.desc = folderDescription 
  this.hreference = hreference 
  this.id = -1   
  this.navObj = 0  
  this.iconImg = 0  
  this.nodeImg = 0  
  this.isLastNode = 0 
 
  //dynamic data 
  this.isOpen = true 
  this.iconSrc = "ftv2folderopen.gif"   
  this.children = new Array 
  this.nChildren = 0 
 
  //methods 
  this.initialize = initializeFolder 
  this.setState = setStateFolder 
  this.addChild = addChild 
  this.createIndex = createEntryIndex 
  this.escondeBlock = escondeBlock
  this.esconde = escondeFolder 
  this.mostra = mostra 
  this.renderOb = drawFolder 
  this.totalHeight = totalHeight 
  this.subEntries = folderSubEntries 
  this.outputLink = outputFolderLink 
  this.blockStart = blockStart
  this.blockEnd = blockEnd
} 
 
//Rendering function for class folder:

function drawFolder(leftSide) 
{ 
  var idParam = "id='folder" + this.id + "'"

  if (browserVersion == 2) { 
    if (!doc.yPos) 
      doc.yPos=20 
  } 

  this.blockStart("folder")

  doc.write("<tr><td>") 
  doc.write(leftSide) 
  this.outputLink() 
  doc.write("<img id='folderIcon" + this.id + "' name='folderIcon" + this.id + "' src='" + this.iconSrc+"' border=0></a>") 
  doc.write("</td><td valign=middle nowrap>") 
  if (USETEXTLINKS) 
  { 
    this.outputLink() 
    doc.write(this.desc + "</a>") 
  } 
  else 
    doc.write(this.desc) 
  doc.write("</td>")  

  this.blockEnd()
 
  if (browserVersion == 1) { 
    this.navObj = doc.all["folder"+this.id] 
    this.iconImg = doc.all["folderIcon"+this.id] 
    this.nodeImg = doc.all["nodeIcon"+this.id] 
  } else if (browserVersion == 2) { 
    this.navObj = doc.layers["folder"+this.id] 
    this.iconImg = this.navObj.document.images["folderIcon"+this.id] 
    this.nodeImg = this.navObj.document.images["nodeIcon"+this.id] 
    doc.yPos=doc.yPos+this.navObj.clip.height 
  } else if (browserVersion == 3) { 
    this.navObj = doc.getElementById("folder"+this.id)
    this.iconImg = doc.getElementById("folderIcon"+this.id) 
    this.nodeImg = doc.getElementById("nodeIcon"+this.id)
  } 
}