javascript - “TypeError:无法读取未定义的属性'balance'”。不确定出什么问题

运行它时，出现“ TypeError：无法读取未定义的属性'balance'”。
我是初次接触Node的人，我不确定自己做错了什么。请帮忙。

它与范围有关吗？我应该如何解决？

//create an accounts array:
var accounts = [];

// create a function that allows you to create an account, passing it an account object:
function createAccount(account)
{
	accounts.push(account);
	return account;
}

// create a function that allows you to lookup an account by passing it a username:
function getAccount(userName)
{
	var matchedAccount;

	for (var i = 0; i < accounts.length; i++)
	{
		if (accounts[i] === userName)
		{
			matchedAccount = accounts[i];
		}
	}

	return matchedAccount;
}

 // create a function called deposit:
 function deposit(account, amount)
 {
	 if (typeof amount === "number")
	 {
		 account.balance = (account.balance + amount);
	 }
	 else
	 {
		 console.log("Deposit failed. Amount is not a number.")
	 }
 }

 // create a function called withdrawal:
 function withdraw(account, amount)
 {
	 if (typeof amount === "number")
	 {
		 account.balance = (account.balance - amount);
	 }
	 else
	 {
		 console.log("Withdraw failed. Amount is not a number.")
	 }
 }

 // create a function called getBalance, which will return the current balance of the account passed to it:
 function getBalance(account)
 {
	 return account.balance;
 }

 function createBalanceGetter(account)
 {
	 return function()
	 {
		 return account.balance;
	 }
 }

 var jessica = createAccount(
 {
	 userName: "Jessica",
	 balance: 0
 });

 deposit(jessica, 120);
 withdraw(jessica, 10);

var jessica2 = getAccount("Jessica");
var getJessica2Balance = createBalanceGetter(jessica2);

console.log(getJessica2Balance());

 

最佳答案

在您的getAccount中，您必须搜索accounts[i].userName，而不仅仅是accounts[i]。将getAccount函数更改为此：

function getAccount(userName)
{
    var matchedAccount;

    for (var i = 0; i < accounts.length; i++)
    {
        if (accounts[i].userName === userName)
        {
            matchedAccount = accounts[i];
        }
    }

    return matchedAccount;
}

现在，这将对每个帐户进行线性搜索，并将该帐户的userName与给定的用户名进行比较。之前，您将一个account对象与一个字符串进行比较，这是不正确的。这导致createBalanceGetter尝试访问undefined.balance，这给出了错误。这是fiddle。