The Tor Browser / file revision

 /* The Great Computer Language Shootout

    http://shootout.alioth.debian.org/

    contributed by Isaac Gouy */

 function TreeNode(left,right,item){

    this.left = left;

    this.right = right;

    this.item = item;

 }

 TreeNode.prototype.itemCheck = function(){

    if (this.left==null) return this.item;

    else return this.item + this.left.itemCheck() - this.right.itemCheck();

 }

 function bottomUpTree(item,depth){

    if (depth>0){

       return new TreeNode(

           bottomUpTree(2*item-1, depth-1)

          ,bottomUpTree(2*item, depth-1)

          ,item

       );

    }

    else {

       return new TreeNode(null,null,item);

    }

 }

 var ret;

 for ( var n = 4; n <= 7; n += 1 ) {

     var minDepth = 4;

     var maxDepth = Math.max(minDepth + 2, n);

     var stretchDepth = maxDepth + 1;

     var check = bottomUpTree(0,stretchDepth).itemCheck();

     var longLivedTree = bottomUpTree(0,maxDepth);

     for (var depth=minDepth; depth<=maxDepth; depth+=2){

         var iterations = 1 << (maxDepth - depth + minDepth);

         check = 0;

         for (var i=1; i<=iterations; i++){

             check += bottomUpTree(i,depth).itemCheck();

             check += bottomUpTree(-i,depth).itemCheck();

         }

     }

     ret = longLivedTree.itemCheck();

 }

 assertEq(ret, -1)