通过调用 javascript class 的 object 在内部调用 function。 我想通过调用 class object 来打印优先队列数组

Question

Here is my Sample Code

class PriorityQueue {
  constructor() {
    this.items = [];
  }
  
  isEmpty() {
    if (this.items.length === 0) return true;
    return false;
  }

  hasValue(element) {
    return this.items.some((item) => item[0] === element);
  }
  peek() {
    this.isEmpty() 
    return this.items[0];
  }
  poll() {
    this.isEmpty() 
    return this.items.splice(0, 1);
  }
  add(number, priority) {
    if (priority===undefined) return this.items.push({ element: number, priority: null });
    if(this.isEmpty() || this.items[this.items.length-1].priority<priority)
    return this.items.push({ element: number, priority: priority })
    for (let i = this.items.length-1; i >= 0; i--) {
      if (this.items[i].priority <= priority)
        return this.items.splice(i+1 , 0, { element: number, priority: priority });
    }
    return this.items.splice(0 , 0, { element: number, priority: priority });
  }
  printAll(){
      return this.items.map(item=>item.element)
  }
}
var priorityQueue= new PriorityQueue();
priorityQueue.add(10, 1);
console.log(Array.from(priorityQueue.printAll())) // [10]
priorityQueue.add(100, 0);
console.log(Array.from(priorityQueue.printAll())) // [100,10]
priorityQueue.add(200, 0);
console.log(Array.from(priorityQueue.printAll())) // [100,200,10]

But what I want priorityQueue object calls printAll() function inside the class. Is it possible? Can we handle with proxies? This is what I want below

 var priorityQueue= new PriorityQueue();
    priorityQueue.add(10, 1);
    console.log(Array.from(priorityQueue)) // [10]
    priorityQueue.add(100, 0);
    console.log(Array.from(priorityQueue)) // [100,10]
    priorityQueue.add(200, 0);
    console.log(Array.from(priorityQueue)) // [100,200,10]

Answer 1

Array.from uses Symbol.iterator , so you can just define that with a generator function :

class PriorityQueue {
  // other functions
  *[Symbol.iterator]() {
    for (const item of this.items) {
      yield item.element;
    }
  }
}

Answer 2

No, a proxy won't help with anything here.

The Array.from method converts an iterable object to an array, so what you want to do is to implement the iterable protocol on your priority queue instances:

class PriorityQueue {
  constructor() {
    this.items = [];
  }
  …
  *[Symbol.iterator]() {
    for (const item of this.items) {
      yield item.element;
    }
  }
  // Alternatively:
  // [Symbol.iterator]() {
  //   return this.items.map(item => item.element).values()
  // }
}