Queue (Ring Queue)

queue.js

class QueueOverflow extends Error {}

class MyQueue {
  constructor(capacity) {
    this.array = [];
    this.head = 0;
    this.tail = 0;
    this.capacity = capacity;
  }
  isEmpty() {
    return this.head == this.tail && this.array[this.head] === undefined;
  }
  isFull() {
    return this.head == this.tail && this.array[this.tail] !== undefined;
  }
  peek() {
    return this.array[this.head];
  }
  __nextHead() {
    return (this.head + 1) % this.capacity;
  }
  __nextTail() {
    return (this.tail + 1) % this.capacity;
  }
  enqueue(value) {
    if (this.isFull()) {
      throw new QueueOverflow();
    }
    this.array[this.tail] = value;
    this.tail = this.__nextTail();
    return this;
  }
  dequeue() {
    if (this.isEmpty()) {
      return undefined;
    }
    this.array[this.head] = undefined;
    this.head = this.__nextHead();
    return this;
  }
}