js实现一个队列的方法

1.队列是遵循先进先出（FIFO)原则的一组有序的项，队列在尾部添加元素，并从顶部移除元素，最新添加的元素必须排在队列的末尾。生活中常见的例子如排队等。

2.创建一个队列类

class Queue{
  constructor(){
    this.count = 0;//记录队列的数量
    this.lowestCount = 0;//记录当前队列头部的位置
    this.items = [];//用来存储元素。
  }
}

3.添加元素

enqueue(element){
   this.items[this.count] = element;
   this.count++;
 }

4.删除元素（只删除队列头部）

dequeue(){
    if(this.isEmpty()){
      return 'queue is null';
    }
    let resulte = this.items[this.lowestCount];
    delete this.items[this.lowestCount];
    this.lowestCount++;
    return resulte;
}

5.查看队列头部元素

peek(){
  return this.items[this.lowestCount];
}

6.判断队列是否为空

isEmpty(){
  return this.count - this.lowestCount === 0;
}

7.清除队列的元素

clear(){
  this.count = 0;
  this.lowestCount = 0;
  this.items = [];
}

8.查看队列的长度

size(){
   return this.count - this.lowestCount;
 }

9.查看队列的所有内容

toString(){
    if(this.isEmpty())return "queue is null";
    let objString = this.items[this.lowestCount];
    for(let i = this.lowestCount+1; i < this.count;i++){
      objString = `${objString},${this.items[i]}`;
    }
    return objString;
}

10.完整代码

class Queue{
  constructor(){
    this.count = 0;//记录队列的数量
    this.lowestCount = 0;//记录当前队列顶部的位置
    this.items = [];//用来存储元素。
  }
  enqueue(element){
    this.items[this.count] = element;
    this.count++;
  }
  dequeue(){
    if(this.isEmpty()){
      return 'queue is null';
    }
    let resulte = this.items[this.lowestCount];
    delete this.items[this.lowestCount];
    this.lowestCount++;
    return resulte;
  }
  peek(){
    return this.items[this.lowestCount];
  }
  isEmpty(){
    return this.count - this.lowestCount === 0;
  }
  size(){
    return this.count - this.lowestCount;
  }
  clear(){
    this.count = 0;
    this.lowestCount = 0;
    this.items = [];
  }
  toString(){
    if(this.isEmpty())return "queue is null";
    let objString = this.items[this.lowestCount];
    for(let i = this.lowestCount+1; i < this.count;i++){
      objString = `${objString},${this.items[i]}`;
    }
    return objString;
  }
}

11.运行结果