classStack{constructor(){this.items=[];}push(item){this.items.push(item);}pop(){返回this.items.pop();}//返回顶部元素，但未修改peek(){returnthis.items.at(-1);}isEmpty(){返回this.items.length===0;}clear(){this.items=[];}size(){返回this.items.length;}toString(){如果(this.isEmpty()){返回“”；}让objString=`${this.items[0]}`;for(leti=1;i
