javascript中未定义街道错误

Question

我是 Javascript 的初学者，我有以下代码：

let address = {

  street: 'Brighton',

  city: 'NY',

  zipcode: 121212,

  showAddress() {

    console.log(street + ' ' + city + ' ' + zipcode);// here is the issue I cannot understand why

  }

}

let address1 = address.showAddress(); 

上面的代码显示一个错误

未捕获的 ReferenceError：街道未在 Object.showAddress 中定义