http://www.cnblogs.com/webFro...上面這篇文章中的先序排列的非遞歸算法如下:BinaryTree.prototype.preOrder_stack = function (visit) {        var stack = new Stack();        stack.push(this);         while (stack.top) {            var p;            // 向左走到盡頭             while ((p = stack.peek())) {                 p.data && visit(p.data);                stack.push(p.leftChild);             }            stack.pop();            if (stack.top) {                 p = stack.pop();                stack.push(p.rightChild);             }         }     };var stack = new Stack();這句是什么意思?。縎tack對(duì)象沒(méi)有定義啊！難道是內(nèi)置對(duì)象？stack.top也不懂……