var credit = 10;

function Item(name) {
  this.name = "";

}

function Vending_item(name,price,id) {
    Item.call(this,name);
    this.price = price;
    this.id = id;
}
Vending_item.prototype = new Item();
Vending_item.prototype.constructor = Vending_item;

var Crisps = new Vending_item("Walkers Ready Salted Crisps",2,01);
var Fizzy1 = new Vending_item("Coca-Cola",1.75,12);
var ChocolateBar = new Vending_item("Dairy Milk",1.25,23);
var ChocolateBar2 = new Vending_item("Twix",34);
var Water = new Vending_item("Buxton Spring Water",1.50,45);
var Fizzy2 = new Vending_item("Fanta Orange",56);
var JumboChocolate = new Vending_item("Double Twix",3,67);

const readline = require('readline');
const purchaseItem = readline.createInterface({input : process.stdin,output : process.stdout});

purchaseItem.question('Please input the ID of the item you would like to Purchase\n',(userInput)=>{
    if(userInput.trim() == Crisps.id){
        credit = credit - Crisps.price;
        console.log("You now have £" + credit + " to spend");
        purchaseItem.question('Would you like to refund this item?\n',(userInput)=>{
            if(userInput.trim() == 'Yes'){
                credit = credit + Crisps.price;
                console.log("You now have £" + credit + " to spend")
                purchaseItem.setPrompt('Would you like to purchase another item?');
                purchaseItem.prompt();
                purchaseItem.on('line',(userInput)=>{
                    if(userInput.trim() == 'Yes'){
                        purchaseItem.setPrompt("Please input another item ID\n");
                        purchaseItem.prompt();
                    }else
                        purchaseItem.close();
                });
             }
        });
     }
});

purchaseItem.on('close',()=>{
      console.log('Thanks for using my vending machine');
});

因此，我建立了一个基本的对象类，有一个变量“ credit”，然后有了我的实际对象。我要求用户输入对象“ crisps”的ID，然后输入该对象应有机会退还该物品，如果是，他们将退还款项，如果没有，则将询问他们是否他们想购买另一种物品。

问题出在这里，当被问到是否要购买另一件商品时，我希望我的程序将其返回到最初的问题：“请输入要购买的商品的ID”，但是我不知道怎么办。

任何帮助将不胜感激。