1.  // 节点类
    2.         function Node(val) {
    3.             this.val = val
    4.             this.next = null
    5.         }
    7.         // 链表类
    8.         function NodeList() {
    9.             this.head = null
    10.             this.length = 0
    11.             // 向链表末尾追加元素
    12.             this.push = push
    13.             // 在值为 val 的节点后面添加一个值为 newVal 的节点
    14.             this.insertAfter = insertAfter
    15.             // 在链表中查找值为 val 的节点
    16.             this.find = find
    17.             // 在链表中查找值为val 的节点的前一个节点
    18.             this.findPrev = findPrev
    19.             // 删除链表中值为 val 的节点
    20.             this.remove = remove
    21.             // 将值为val 的节点修改为 newVal
    22.             this.update = update
    23.             // 打印链表
    24.             this.toString = toString
    25.         }
    28.         function push(val) {
    30.             let node = new Node(val)
    31.             // 第一个节点
    32.             if (this.head === null) {
    33.                 this.head = node
    34.             } else {
    35.                 let current = this.head
    36.                 // 找到最后一个节点
    37.                 while (current.next !== null) {
    38.                     current = current.next
    39.                 }
    40.                 // 最后一个节点后面追加节点
    41.                 current.next = node
    42.             }
    44.             this.length++
    45.         }
    47.         function insertAfter(val, newVal) {
    49.             let current = this.find(val)
    50.             if (current === null) return -1
    51.             let node = new Node(newVal)
    52.             // 先将当前节点的指向给到新节点的指向 ！
    53.             node.next = current.next
    54.             // 再将当前节点指向新节点
    55.             current.next = node
    56.             this.length++
    58.         }
    61.         function find(val) {
    63.             // 空链表
    64.             if (this.head === null) return null
    65.             let current = this.head
    66.             // 查找到最后一个节点之前
    67.             while (current.next !== null) {
    68.                 if (current.val === val) return current
    69.                 current = current.next
    70.             }
    71.             // 判断最后1个节点
    72.             if (current.val === val) return current
    73.             return null
    74.         }
    76.         function findPrev(val) {
    78.             // 空链表或者查找第一个节点的前一个节点均查不到
    79.             if (this.head === null || this.head.val === val) return null
    80.             let current = this.head
    81.             // 最后一个节点不进循环, 最后一个节点不可能是某个节点的前一个节点
    82.             while (current.next !== null) {
    83.                 if (current.next.val === val) return current
    84.                 current = current.next
    85.             }
    86.             return null
    87.         }
    89.         function remove(val) {
    91.             let current = this.find(val)
    92.             if (current === null) return -1
    93.             else {
    94.                 let prev = this.findPrev(val)
    95.                 if (prev !== null) {
    96.                     prev.next = current.next
    97.                 } else { 
    98.                     // prev === null 即删第一个节点 让当前节点的下一个节点第2个节点为头
    99.                     this.head = current.next
    100.                 }
    101.             }
    102.             this.length--
    104.         }
    106.         function update(val, newVal) {
    108.             let current = this.find(val)
    109.             if (current === null) return -1
    110.             current.val = newVal
    112.         }
    114.         function toString() {
    116.             let current = this.head
    117.             let str = ''
    118.             let index = 0
    119.             while (current !== null) {
    120.                 // str += index + current.val + (current.next ? ' -> ' : '')
    121.                 str += `(${index}) ${current.val}${current.next ? ' -> ' : ''}`
    122.                 current = current.next
    123.                 index++
    124.             }
    125.             console.log(str)
    127.         }
    130.         // 测试代码
    132.         let nodeList = new NodeList()
    134.         nodeList.push('1st element')
    135.         nodeList.push('2nd element')
    136.         nodeList.push('3rd element')
    137.         nodeList.push('4th element')
    139.         console.log('find', nodeList.find('1st element'))
    140.         console.log('find', nodeList.find('2nd element'))
    141.         console.log('find', nodeList.find('3rd element'))
    142.         console.log('find', nodeList.find('4th element'))
    144.         console.log('findPrev', nodeList.findPrev('1st element'))
    145.         console.log('findPrev', nodeList.findPrev('2nd element'))
    146.         console.log('findPrev', nodeList.findPrev('3rd element'))
    147.         console.log('findPrev', nodeList.findPrev('4th element'))
    149.         nodeList.remove('4th element')
    150.         console.log('length', nodeList.length, 'nodeList', nodeList)
    152.         nodeList.insertAfter('2nd element', '2nd element 2')
    153.         console.log('length', nodeList.length, 'nodeList', nodeList)
    155.         nodeList.update('2nd element', '2nd element update')
    156.         console.log('length', nodeList.length, 'nodeList', nodeList)
    158.         nodeList.toString()
    160.      //   原文链接：https://blog.csdn.net/aSmallProgrammer/article/details/106137774