Javascript For/in 循环不工作 - 对象属性未定义错误

Question

所以我正在学习我正在学习的课程中的一个简单的 For/in 循环练习。我们有一个具有 3 个属性的简单对象，我们必须创建一个带有 2 个参数的函数 - 对象名称和您要查找的项目。

我做了我的功能和老师的解决方案进行了比较，它完全一样。问题是当我在控制台中尝试时，我收到一个错误，指出对象属性未定义。

代码如下：

// Question #2:
// Write a function checkBasket() that lets you know if the item is in the basket or not
const amazonBasket = {
  glasses: 1,
  books: 2,
  floss: 100
}

function checkBasket(basket, lookingFor) {
  for(item in basket) {
    console.log(item);
     if(item === lookingFor) {
      return `${lookingFor} is in your basket`;
    }     
   }
   return `${lookingfor} is not in your basket`;
}

非常感谢大家的帮助！这是一个艰难但愉快的学习过程！

谢谢！

Answer 1

您的代码按我的预期工作，所以问题可能出在您调用函数的方式或代码中未显示的内容。

PS：如果您使用数组而不是对象来存储项目，则可以使用 array.find() 或 array.indexOf() 等来操作篮子更简单。

// Question #2:
// Write a function checkBasket() that lets you know if the item is in the basket or not
const amazonBasket = {
  glasses: 1,
  books: 2,
  floss: 100
}

function checkBasket(basket, lookingFor) {
  for(item in basket) {
    console.log(item);
     if(item === lookingFor) {
      return `${lookingFor} is in your basket`;
    }     
   }
   return `${lookingFor} is not in your basket`;
}

console.log( checkBasket( amazonBasket, 'floss' ));
console.log( checkBasket( amazonBasket, 'books' ));
console.log( checkBasket( amazonBasket, 'glasses' ));

const amazonBasket = [
  { "order_id": 1, "product_id": 13341544, "product_name": "glasses", "quantity": 1 },
  { "order_id": 1, "product_id": 12121321, "product_name": "books", "quantity": 5 },
  { "order_id": 1, "product_id": 47254114, "product_name": "floss", "quantity": 100 }
];

const checkBasket = ( basket, lookingFor ) => {
  const item = basket.find( item => item.product_name === lookingFor );
  if ( item ) return `${lookingFor} is in your basket`;
  else return `${lookingFor} is not in your basket`;
};

console.log( checkBasket( amazonBasket, 'floss' ));
console.log( checkBasket( amazonBasket, 'books' ));
console.log( checkBasket( amazonBasket, 'glasses' ));

Answer 2

您的代码在最后一行有错字：lookingfor 而不是 lookingFor

Answer 3

刚刚学习到课程的这一部分。该对象应该是一个字符串。试试这样，把代码放好后，调用函数是这样的：

checkBasket(amazonBasket, 'books')

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