JavaScript数据结构单向链表的方法封装

    function LinkedList() {
      function Node(data){
        this.data = data
        this.next = null
      }
      this.head = null;
      this.length = 0;
      LinkedList.prototype.append = function (data) {
        var newNode = new Node(data)
        if (this.head === null) {
          this.head = newNode
        }else{
          var current = this.head
          while(current.next !== null){
            current = current.next
          }
          current.next = newNode
        }
        this.length++
      }
      LinkedList.prototype.toString = function () { 
        var current = this.head
        var listString = ''
        while(current){
          listString += current.data + ' '
          current = current.next
        }
        return listString
      }
      LinkedList.prototype.insert = function (data, position) { 
        if (position < 0 || position > this.length) return false
        var newNode = new Node(data)
        if (position == 0) {
          newNode.next = this.head
          this.head = newNode
        }
        else{
          var index = 0
          var current = this.head
          var previous = null
          while(index++ < position){
            previous = current
            current = current.next
          }
          newNode.next = current
          previous.next = newNode
        }
        this.length += 1
        return true
      }
      LinkedList.prototype.get = function(position) {
        if (position <0 || position >= this.length) return null
        var index = 0
        var current = this.head
        while(index++<position) {
          current = current.next
        }
        return current.data
      }
      LinkedList.prototype.indexOf = function(data) {
        var index = 0
        var current = this.head
        while (current){
          if (current.data === data) {
            return index
          }
          current = current.next
          index++
        }
        return -1
      }
      LinkedList.prototype.update = function(position, data) {
        if (position <0 || position >= this.length) return false
        var current = this.head
        var index = 0
        while(current) {
          current = current.next
          index++
          if (index === position) {
            current.data = data
            return
          }
        }
        return -1
      }
      LinkedList.prototype.removeAt = function(position) {
        if (position < 0 || position >= this.length) return false
        var current = this.head
        var index = 0
        var previous = null
        if (position == 0) {
          this.head = this.head.next
        }else {
          while (index++ < position) {
            previous = current
            current = current.next
          }
          previous.next = current.next
        }
        this.length -=1
        return current.data
      }
      LinkedList.prototype.remove = function (data) {
        var position = this.indexOf(data)
        return this.removeAt(position)
      }
      LinkedList.prototype.isEmpty = function() {
        return this.length == 0
      }
      LinkedList.prototype.size = function() {
        return this.length
      }
      LinkedList.prototype.toString = function() {
        var listString = ''
        var index = 0
        var current = this.head
        while(index++ < this.length){
          listString += current.data + ','
          current = current.next
        }
        return listString
      }
    }