var timerlen = 5;
var slideAniLen = 150;

var timerID = new Array();
var startTime = new Array();
var obj = new Array();
var endHeight = new Array();
var moving = new Array();
var dir = new Array();

function slidedown(subnav){
  if(moving[subnav])
    return;
 
  if(document.getElementById(subnav).style.display != "none")
    return; // cannot slide down something that is already visible
 
  moving[subnav] = true;
  dir[subnav] = "down";
  startslide(subnav);
}
 
function slideup(subnav){
  if(moving[subnav])
    return;
 
  if(document.getElementById(subnav).style.display == "none")
    return; // cannot slide up something that is already hidden
 
  moving[subnav] = true;
  dir[subnav] = "up";
  startslide(subnav);
}

function startslide(subnav){
  obj[subnav] = document.getElementById(subnav);
 
  endHeight[subnav] = parseInt(obj[subnav].style.height);
  startTime[subnav] = (new Date()).getTime();
 
  if(dir[subnav] == "down"){
    obj[subnav].style.height = "1px";
  }
 
  obj[subnav].style.display = "block";
 
  timerID[subnav] = setInterval('slidetick(\'' + subnav + '\');',timerlen);
}

function slidetick(subnav){
  var elapsed = (new Date()).getTime() - startTime[subnav];
 
  if (elapsed > slideAniLen)
    endSlide(subnav)
  else {
    var d =Math.round(elapsed / slideAniLen * endHeight[subnav]);
    if(dir[subnav] == "up")
      d = endHeight[subnav] - d;
 
    obj[subnav].style.height = d + "px";
  }
 
  return;
}

function endSlide(subnav){
  clearInterval(timerID[subnav]);
 
  if(dir[subnav] == "up")
    obj[subnav].style.display = "none";
 
  obj[subnav].style.height = endHeight[subnav] + "px";
 
  delete(moving[subnav]);
  delete(timerID[subnav]);
  delete(startTime[subnav]);
  delete(endHeight[subnav]);
  delete(obj[subnav]);
  delete(dir[subnav]);
 
  return;
}

function toggleSlide(subnav){
  if(document.getElementById(subnav).style.display == "none"){
    // div is hidden, so let's slide down
    slidedown(subnav);
  }else{
    // div is not hidden, so slide up
    slideup(subnav);
  }
}