关于javascript:基于链表实现的迭代器

最近始终在钻研链表相干的构造，突发奇想实现一下相似数组的entries性能

先贴链表的代码，以单向链表为例

定义

链表存储有序的元素汇合，但不同于数组，链表中的元素在内存中并不是间断搁置的。
每个 元素由一个存储元素自身的节点和一个指向下一个元素的援用(也称指针或链接)组成。
下图展 示了一个链表的构造。

链表节点的类

class Node {  constructor(value) {    this.value = value;    this.next = null;  }}

链表实现类

class LinkList {  constructor() {    this.head = null;    this.count = 0;  }  push(val) {    const node = new Node(val);    if (this.head == null) {      this.head = node;    } else {      let current = this.head;      while (current.next != null) {        current = current.next;      }      current.next = node;    }    this.count++;    return this.count;  }  removeAt(index) {    if (index >= 0 && index < this.count) {      let head = this.head;      if (index === 0) {        this.head = head.next;      } else {        // 上一个        let prev = this.getElementAt(index - 1);        let current = prev.next;        prev.next = current.next;      }      this.count--;      return head.value;    }    return undefined;  }  getElementAt(index) {    if (index >= 0 && index < this.count) {      let current;      if (index === 0) {        current = this.head;      } else {        current = this.head;        for (let i = 0; i < index; i++) {          current = current.next;        }      }      return current;    }    return undefined;  }  insert(element, index) {    if (index >= 0 && index < this.count) {      let node = new Node(element)      if (index === 0) {        node.next = this.head;        this.head = node;      } else {        // 上一个        let prev = this.getElementAt(index - 1);        let next = prev.next;        node.next = next;        prev.next = node;      }      this.count++;      return element;    }    return undefined;  }  indexOf(element) {    let current = this.head;    for (let i = 0; i < this.count; i++) {      if (current.value === element) {        return i;      }      current = current.next;    }    return undefined;  }  getHead() {    return this.head;  }  remove(element) {    const index = this.indexOf(element);    this.removeAt(index);  }  isEmpty() {    return this.size() === 0;  }  size() {    return this.count;  }  toString() {    let current = this.head;    let str = `${current.value}`;    for (let i = 1; i < this.count; i++) {      current = current.next;      str = `${str},${current.value}`;    }    return str;  }}

以原型继承形式实现entries

LinkList.prototype.entries = function() {  let current = this.head;  const count = this.count;  let selfCount = 0;  return new function() {    this.next = function() {      if(selfCount > count || current == null) {        return {value: undefined, done: true};      }      let [index, value] = [selfCount, current.value];      selfCount++;      let done = count === selfCount;      current = current.next;      return {index, value, done};    }  }}

此处采纳闭包是为了获取链表构造的头节点与节点数量，返回构造函数来实现next办法

测试

let l = new LinkList();l.push(1);l.push(2);l.push(3);l.insert(1.5, 1)const item = l.entries();console.log(item.next())console.log(item.next())console.log(item.next())console.log(item.next())console.log(item.next())console.log(item.next())console.log(item.next())console.log(item.next())

此处针对数组返回做了一些改变，将index和value做了独自抽取