链表 是一种物理存储单元上非连续、非顺序的存储结构，它既可以表示线性结构，也可以用于表示非线性结构，数据元素的逻辑顺序是通过链表中的指针链接次序实现的。链表由一系列结点（链表中每一个元素称为结点）组成，结点可以在运行时动态生成。每个结点包括两个部分：一个是存储数据元素的数据域，另一个是存储下一个结点地址的指针域。
function LinkedList() {
function Node(element) {
this.element = element;
this.next = null;
}
var length = 0;
var head = null;
this.append = function(element) {
var node = new Node(element);
if (!head) {
head = node;
} else {
var current = head;
while (current.next) {
current = current.next;
}
current.next = node;
}
length++;
};
this.insert = function(element, position) {
if(!position || !element){
return false;
}
var current = head,
previous = null,
index = 0;
var node = new Node(element);
if(position >= 0 && position <= length-1){
if(position == 0){
node.next = current;
head = node;
}else{
while(index++ < position){
previous = current;
current = current.next;
}
node.next = current;
previous.next = node;
}
length++;
}
};
this.removeAt = function(position) {
var current = head,
previous = null,
index = 0;
if(position >= 0 && position <= length-1){
if(position == 0){
head = current.next;
}else{
while(index++ < position){
previous = current;
current = current.next;
}
previous.next = current.next;
}
length--;
return current.element;
}
};
this.remove = function(element) {
var index = this.indexOf(element);
return this.removeAt(index);
};
this.indexOf = function(element) {
var current = head,
index = 0;
while(current){
if(element == current.element){
return index;
}
index++;
current = current.next;
}
return -1;
};
this.isEmpty = function() {
return length == 0;
};
this.size = function() {
return length;
};
this.getHead = function() {
return head.element;
};
this.toString = function() {
var current = head;
var s = "";
while(current){
s += (","+current.element);
current = current.next;
}
return s.substr(1);
};
this.print = function() {
console.log(this.toString())
};
}