源码共读，第32期 | yocto-queue队列链表

1.前言

• 本文参加了由公众号@若川视野 发起的每周源码共读活动，   点击了解详情一起参与。
• 这是源码共读的第32期，链接：yocto-queue 队列 链表

2.yocto-queue了解

1. 对大的数组上进行操作，考虑使用yocto-queue 来替代 Array，而不是采用 Array.push 和 Array.shift
2. 队列是元素的有序列表，其中元素插入到队列的末尾并从队列的前面删除。队列基于先进先出 （FIFO） 原则工作
3. 了解时间复杂度、空间复杂度
4. 又熟悉了es6 class 私有属性、私有方法
5. 熟悉Iterator Generator

3.源码

How it works:
`this.#head` is an instance of `Node` which keeps track of its current value and nests another instance of `Node` that keeps the value that comes after it. When a value is provided to `.enqueue()`, the code needs to iterate through `this.#head`, going deeper and deeper to find the last value. However, iterating through every single item is slow. This problem is solved by saving a reference to the last value as `this.#tail` so that it can reference it to add a new value.
*/

class Node {
	value;
	next;

	constructor(value) {
		this.value = value;
	}
}

export default class Queue {
        //es6 私有属性前边采用#表示，只能在内部使用
	#head;
	#tail;
	#size;

	constructor() {
        //初始化清空当前当前属性 并让siez=0
		this.clear();
	}

	enqueue(value) {
		const node = new Node(value);
                //进行判断是否第一次添加
		if (this.#head) {
                //这块看起来最开始不明白看了其他笔记 才有点理解为啥这么写了
			this.#tail.next = node;
			this.#tail = node;
		} else {
			this.#head = node;
			this.#tail = node;
		}

		this.#size++;
	}
        //删除链表从头部开始删除
	dequeue() {
		const current = this.#head;
		if (!current) {
			return;
		}

		this.#head = this.#head.next;
		this.#size--;
		return current.value;
	}
        //清空整个链表
	clear() {
		this.#head = undefined;
		this.#tail = undefined;
		this.#size = 0;
	}
        //获取链表长度
	get size() {
		return this.#size;
	}

	* [Symbol.iterator]() {
		let current = this.#head;

		while (current) {
			yield current.value;
			current = current.next;
		}
	}
}