js实现栈的方法

class Stack {
  constructor() {
    this.items = [];
  }

  push(item) {
    this.items.push(item);
  }

  pop() {
    return this.items.pop();
  }

  // 返回顶部元素，但是不修改
  peek() {
    return this.items.at(-1);
  }

  isEmpty() {
    return this.items.length === 0;
  }
  clear() {
    this.items = [];
  }
  size() {
    return this.items.length;
  }

  toString() {
    if (this.isEmpty()) {
      return "";
    }
    let objString = `${this.items[0]}`;
    for (let i = 1; i < this.count; i++) {
      objString = `${objString},${this.items[i]}`;
    }
    return objString;
  }
}

js实现队列的方法

class Queue {
  constructor() {
    this.count = 0;
    this.lowestCount = 0;
    this.items = {};
  }

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

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

  dequeue() {
    if (this.isEmpty()) {
      return void 0;
    }
    const result = this.items[this.lowestCount];
    delete this.items[this.lowestCount];
    this.lowestCount++;
    return result;
  }