es6 实现单链表

第一种
/**
 * 链表节点类
 */
class Node {
    constructor(ele) {
        this.ele = ele;
        this.next = null;
    }
}
/**
 * 链表类
 */
class NodeList {
    constructor(ele) {
        this.head = new Node(ele); //初始化链表的头节点
    }
    findPreNode(item) {
        let currentNode = this.head;
        while (currentNode && currentNode.next && currentNode.next.ele !== item) {
            if (currentNode.next) {
                currentNode = currentNode.next;
            } else {
                currentNode = null;
            }

        }
        return currentNode;
    }
    findNode(item) {
        let currentNode = this.head;

        while (currentNode && currentNode.ele !== item) {
            if (currentNode.next) {
                currentNode = currentNode.next;
            } else {
                currentNode = null;
            }
        }

        return currentNode;
    }
    findLastNode() {
        let currentNode = this.head;
        while (currentNode.next) {
            currentNode = currentNode.next;
        }
        return currentNode;
    }
    append(newItem, preItem) {
        let newNode = new Node(newItem);
        if (preItem) { //  判读是否是插入到指定节点后面，如果不是则插入到最后一个节点。
            let currentNode = this.findNode(preItem);
            newNode.next = currentNode.next;
            currentNode.next = newNode;
        } else {
            let lastNode = this.findLastNode();
            lastNode.next = newNode;
        }
    }
    remove(item) {
        let preNode = this.findPreNode(item); //  找到前一节点，将前一节点的next指向该节点的next
        if (preNode.next != null) {
            preNode.next = preNode.next.next;
        }
    }
    toString() {
        let currentNode = this.head;

        let strList = [];
        while (currentNode.next) {
            strList.push(JSON.stringify(currentNode.ele));
            currentNode = currentNode.next;
        }
        strList.push(JSON.stringify(currentNode.ele));

        return strList.join(' ==> ')
    }
 /* 逆置分析

     单链表分为带头节点和不带头节点两种，逆置思路有两种，第一种是采用头插法重新建立新的单链表，该方法直接遍历链表，每次将当前结点添加到新链表的头部；第二种是通过该表*next指针，定义三个指针*pre, *p, *r，分别表示三个连续结点，将p->next指向pre，但       同时p的后继节点会断开，所以需要用r保存其后继节点。

   */

// 头插法
  reverse () {
    let p = null;
    let current = this.head;
    while (current !== null) {
      const temp = current.next;
      current.next = p;
      p = current;
      current = temp;
    }
    return p;
  }

  // 1 -> 2 -> 3 -> 4
  // r
  // 修改*next指针
  reverse2 () {
    let pre = null;
    let p = null;
    let r = null;
    r = this.head;
    while (r !== null) {
      if (p === null) {
        p = r;
        r = r.next;
        p.next = null;
        continue;
      }
      pre = p;
      p = r;
      r = r.next;
      p.next = pre;
    }
    return p;
  }
}
let A = { name: 'A', age: 10 },
    B = { name: 'B', age: 20 },
    C = { name: 'C', age: 30 },
    D = { name: 'D', age: 40 },
    E = { name: 'E', age: 50 };

let nList = new NodeList(A);

nList.append(C);
nList.append(B);
nList.append(D);
nList.append(E, A);
console.log(" " + nList);
nList.remove(C);
console.log(" now " + nList)

origin: {"name":"A","age":10} ==> {"name":"E","age":50} ==> {"name":"C","age":30} ==> {"name":"B","age":20} ==> {"name":"D","age":40}
 now: {"name":"A","age":10} ==> {"name":"E","age":50} ==> {"name":"B","age":20} ==> {"name":"D","age":40}

第二种
/**
 * 链表节点类
 */
class Node {
  constructor (ele) {
    this.ele = ele;
    this.next = null;
  }
}
/**
 * 链表类
 */
class NodeList {
  constructor (ele) {
    this.head = null; // 初始化链表的头节点
    this.lenght = 0;
  }
  /**
                     *  尾部插入数据
                     * @param {*} ele
                     */
  append (ele) {
    let newNode = new Node(ele);
    let currentNode;
    if (this.head === null) {
      this.head = newNode;
    } else {
      currentNode = this.head;
      while (currentNode.next) {
        currentNode = currentNode.next;
      }
      currentNode.next = newNode;
    }
    this.lenght++;
  }/**
   * 项链表某个位置插入元素
   * @param {*} position
   * @param {*} ele
   */
  insert (position, ele) {
    if (position >= 0 && position <= this.lenght) {
      let newNode = new Node(ele);
      let currentNode = this.head;
      let pre;
      let index = 0;
      if (position === 0) {
        newNode.next = currentNode;
        this.head = newNode;
      } else {
        while (index < position) {
          pre = currentNode;
          currentNode = currentNode.next;
          index++;
        }
        newNode.next = currentNode;
        pre.next = newNode;
      }
      this.lenght++;
    } else {
      return new Error('位置超出范围');
    }
  }
  removeAt (position) {
    if (position >= 0 && position < this.lenght) {
      let currentNode = this.head;
      let pre;
      let index = 0;
      if (position === 0) {
        this.head = currentNode.next;
      } else {
        while (index < position) { // 1,2,3
          pre = currentNode;
          currentNode = currentNode.next;
          index++;
        }
        pre.next = currentNode.next;
      }
      this.lenght--;
    } else {
      return new Error('删除位置有误');
    }
  }
  find (ele) {
    let currentNode = this.head;
    let index = 0;
    while (currentNode) {
      if (JSON.stringify(currentNode.ele) === JSON.stringify(ele)) {
        return index;
      } else {
        index++;
        currentNode = currentNode.next;
      }
    }
    return -1;
  }
  // 判断链表是否为空
  isEmpty () {
    return this.length === 0;
  }
  size () {
    return this.length;
  }
  // 返回头
  getHead () {
    return this.head;
  }
  toString () {
    let current = this.head;
    let str = '';
    while (current) {
      str += JSON.stringify(current.ele) + ' => ';
      current = current.next;
    }
    return str;
  }
}
let A = { name: 'A', age: 10 };

let B = { name: 'B', age: 20 };

let C = { name: 'C', age: 30 };

let D = { name: 'D', age: 40 };

let E = { name: 'E', age: 50 };

let nList = new NodeList();

nList.append(A);
nList.append(C);
nList.append(B);
nList.append(D);
nList.append(E);
// console.log(JSON.stringify(nList, null, 2));
console.log(' origin: ' + nList);
nList.removeAt(2);
console.log(' now: ' + nList);

origin: {"name":"A","age":10} => {"name":"C","age":30} => {"name":"B","age":20} => {"name":"D","age":40} => {"name":"E","age":50} =>
now: {"name":"A","age":10} => {"name":"C","age":30} => {"name":"D","age":40} => {"name":"E","age":50} =>

 参照：https://blog.csdn.net/qq_40941722/article/details/94381637