寻求链表节点删除的秘密 !!!
需求: 创建双向链表, 把双向链表清空
思路: 利用链表节点前后相继的特性, 逐个解除节点之间的关系, 释放节点. 

问题: 如果只是利用前后指针改变彼此关系, 释放某个节点. 没有问题.
逐个改变关系, 做链表清空操作, 失败. 从log来看, 头节点访问到了, 并且也执行了释放的操作. 但是结果显示没有释放. 这个问题和在进行二叉树节点删除的情况相似, 不知道为啥. 郁闷就两个字.  

function twolinkNode(data)
{
this.data = data;
this.next = this.prior = null;
}

/*
 * @breif: doubly linked list
 * @
 */
function Twolink()
{
/*
* @breif: create one doubly linked list based on random number
*/
Twolink.prototype.createTwolink = function(n)
{
var rear;
var q;

if (n == 0) 
this.head = null;
else if (n > 0) 
{
var k = parseInt(Math.random() * 100);
this.head = new twolinkNode(k);
rear = this.head;
this.lastNode = this.head;

for (var i = 1; i < n; i++) 
{
k = parseInt(Math.random() * 100);
q = new twolinkNode(k);
rear.next = q;
q.prior = rear;
rear = q;

}

this.lastNode = rear;
}
}

/*
* @brief: output the link
*/
Twolink.prototype.outputTwoLink = function(curNode, direction)
{
while (curNode != null)
{
document.write(curNode.data + "--->");
if (direction == "head") 
curNode = curNode.next;
else if (direction == "last") 
curNode = curNode.prior;
}
}



/*
* @brief: appends the specified element to the end of the list
* @return: true if successful, fals if failed
*/
Twolink.prototype.add = function(dElement)
{
var q = new twolinkNode(dElement);
this.lastNode.next = q;
q.prior = this.lastNode;

this.lastNode = q;
}

/*
* @brief: remove all of the elements in the list
* 
*/
Twolink.prototype.clear = function() // problem 
{
var tmp;
var count = 0;

while( this.lastNode != null)
{
count ++;

tmp = this.lastNode;

console.log(" [1] count %d last node data %d ",count, this.lastNode.data);
this.lastNode = tmp.prior;
if( this.lastNode != null )
console.log(" [2] count %d last node data %d ", count, this.lastNode.data);
tmp = null;
}
}

/*
 * @brief: removes the element in the specified position
 * @para: position
 * @return: the node in the specified position
 */
Twolink.prototype.remove = function(pos)
{
var tmp;
var n;
var q;

tmp = this.head;
q = tmp;
n=0;

while( n != pos )
{
q = tmp.next;
tmp = q;
n++;
}

/*
* remove the element
*/
if( n == pos )
{
tmp.prior.next = tmp.next;
tmp.next.prior = tmp.prior;
return(tmp);
}
else
return false;
}

}


测试代码: 
document.write("create the list with 6 random number <br>");
t.createTwolink(6);
t.outputTwoLink(t.head, "head");


document.write("<br>remove the data in # 3 <br>");
alert(t.remove(3));
t.outputTwoLink(t.head, "head");


document.write(" <br> insert 5 into the list");
document.write("<br>");
t.add(5);
t.outputTwoLink(t.head,"head");

document.write("<br>");
document.write("execute clear");
t.clea