JavaScript实现基于数组的栈

class StackArray {
  constructor() {
    this.items = [];
  }
  push(element) {
    this.items.push(element);
  }


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





  peek() {
　　return this.items[this.items.length-1];   //如果数组下标为-1，返回值为undefined
  }





  isEmpty() {
    return this.items.length === 0;
  }





  size() {
    return this.items.length;
  }





  clear() {
    this.items = [];   //指向一个新的空数组，原来的数组空间会被JavaScript垃圾会后机制自动回收
  }





  toArray() {
    return this.items;
  }





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