text: class Queue {
  	constructor() {
  		this.items = [];
  	}
  	
  	enqueue(e) {
  		this.items.push(e);
  	}
  	
  	dequeue() {
  		return this.items.shift();
  	}
  	
  	isEmpty() {
  		return this.items.length == 0;
  	}
  	
  	peek() {
  		return !this.isEmpty() ? this.items[0] : undefined;
  	}
  	
  	size() {
  		return this.items.length;
  	}
  }