Bridge ファイル名をバッチで変更で画像をアトランダムに並べたい

function AddRandomRename() 
{
this.menuID = "randomRename";
this.menuCommandID = "RandomRename";
}

AddRandomRename.prototype.run = function() 
{
var retval = true;
if (!this.canRun()) 
{
retval = false;
return retval;
}
var randrename = new MenuElement("command", "Random Rename", "at the end of Tool", "RandomRename");
randrename.onSelect = function () 
{ 
var tg = app.document.selections;
for (var i=0;i<tg.length;i++)
tg[i].name = Math.floor(Math.random()*1000).toString() + i.toString()+"."+tg[i].name.split(".").pop();
return;
}
}

AddRandomRename.prototype.canRun = function() 
{
if (BridgeTalk.appName == "bridge") 
{
if ((MenuElement.find(this.menuID)) 
&& (MenuElement.find(this.menuCommandID))) 
{
alert("menu item aleady exist...");
return false;
}
return true;
}
return false;
}

new AddRandomRename().run();