class Node{
constructor(value){
this.value=value;
this.next=null;
}
}
class Queue{
constructor(){
this.first=null;
this.last=null;
this.length=0;
}
peek(){
return this.first;
}
enqueue(value){
const newNode= new Node(value);
if(this.length===0){
this.first=newNode;
this.last=newNode;
}else{
this.last.next=newNode;
this.last=newNode;
}
this.length++;
return this
}
dequeue(){
if(!this.first){
return null
}
if(this.first===this.last){
this.last=null;
}
const holdingPointer=this.first;
this.first=this.first.next;
this.length--;
return this;
}
}
const q = new Queue()
q.enqueue(4)
q.enqueue(5)
q.enqueue(6)
q.dequeue()
q.dequeue()
q.dequeue()
