双向链表和普通链表的区别在于，在链表中，一个节点只有链向下一个节点的链接，而在双向链表中，链接是双向的：一个链向下一个元素，另一个链向前一个元素。
双向链表提供了两种迭代列表的方法：从头到尾，或者反过来。我们也可以访问一个特定节点的下一个或前一个元素。在单向链表中，如果迭代列表时错过了要找的元素，就需要回到列表起点，重新开始迭代。这是双向链表的一个优点。
双向链表：单向链表只能向着一个方向遍历链表节点，而在节点指针域中增加了前向指针的双向链表，则可以向着两个方向遍历节点。这使得双向链表也可以在任何一个节点遍历整个链表。
function DoublyLinkedList() {
var Node = function(element) {
this.element = element;
this.next = null;
this.prev = null;
};
var length = 0,
head = null,
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this.insert = function(position,element){
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head = node;
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node.prev = current;
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node.next = current;
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current.prev = node;
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};
this.removeAt = function(position){
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index = 0,
previous;
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return current.element;
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};
this.remove = function(element){
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};
this.remove = function(){
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this.indexOf = function(element){
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this.size = function(){
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this.toString = function(){
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this.getHead = function(){
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};
this.getTail = function(){
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};
}
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